9.4 Chemical Monitoring and ManagementContextual Outline

The state of our environment is an impOliant issue for society. Pollution of air, land and water inurban, rural and wilderness areas is a phenomenon that affects the health and survival of allorganisms, including humans. An understanding of the chemical processes involved in interactions inthe full range of global environments, including atmosphere and hydrosphere, is indispensable to anunderstanding of how environments behave and change. It is also vital in understanding howtechnologies, which in part are the result of chemical research, have affected environments. Thismodule encourages discussion of how chemists can assist in reversing or minimising theenvironmental problems caused by technology and the human demand for products and services.

Some modem technologies can facilitate the gathering of infonllation about the occurrence ofchemicals - both those occurring in natural environments and those that are released as a result ofhuman technological activity. Such technologies include systems that have been developed toquantify and compare amounts of substances.

This module increases students' understanding of the nature, practice, applications and uses ofchemistry and the implications of chemistry for society and the environment.

1. Much of the work •of chemistsinvolvesmonitoring thereactants andproducts ofreactions andmanaging •reactionconditions

outline the role of a chemistemployed in a named industry orenterprise, identifying the branch ofchemistry undertaken by the chemistand explaining a chemical principlethat the chemist uses

Students:

• gather, process and presentinformation from secondarysources about the work ofpractising scientistsidentifying:- the variety of chemical

occupationsa specific chemicaloccupation for a moredetailed study

identify the need for collaborationbetween chemists as they collect andanalyse data

• describe an example of a chemicalreaction such as combustion, wherereactants form different productsunder different conditions and thuswould need monitoring

1. Much of the work •of chemistsinvolvesmonitoring thereactants andproducts ofreactions andmanaging •reactionconditions

outline the role of a chemistemployed in a named industry orenterprise, identifying the branch ofchemistry undertaken by the chemistand explaining a chemical principlethat the chemist uses

identify the need for collaborationbetween chemists as they collect andanalyse data

gather, process and presentinformation from secondarysources about the work ofpractising scientistsidentifying:- the variety of chemical

occupationsa specific chemicaloccupation for a moredetailed study

• describe an example of a chemicalreaction such as combustion, wherereactants form different productsunder different conditions and thuswould need monitoring

2. Chemicalprocesses inindustry requiremonitoring andmanagement tomaximiseproduction

Chemistry Stage 6 Syllabus

• identify and describe the industrial uses •of ammonia

• identify that ammonia can besynthesised from its component gases,nitrogen and hydrogen

• describe that synthesis of ammoniaoccurs as a reversible reaction that willreach equilibrium

• identify the reaction of hydrogen withnitrogen as exothermic

• explain why the rate of reaction isincreased by higher temperatures

• explain why the yield of product inthe Haber process is reduced at highertemperatures using Le Chatelier'sprinciple

• explain why the Haber process is basedon a delicate balancing act involvingreaction energy, reaction rate andequilibrium

• explain that the use of a catalyst willlower the reaction temperaturerequired and identify the catalyst(s)used in the Haber process

• analyse the impact of increasedpressure on the system involved in theHaber process

• explain why monitoring of thereaction vessel used in the Haberprocess is crucial and discuss themonitoring required

gather and processinformation from secondarysources to describe theconditions under wh.ich Haberdeveloped the industrialsynthesis of ammonia andevaluate its significance atthat time in world history

2. Chemicalprocesses inindustry requiremonitoring andmanagement tomaximiseproduction

• identify and describe the industrial usesof ammonia

identify that ammonia can besynthesised from its component gases,nitrogen and hydrogen

describe that synthesis of ammonia .occurs as a reversible reaction that wIllreach equilibrium

The formation of ammonia from its constituent elements can be summarised using the followingequation.

This reaction was performed at two different temperatures. The change in the concentration of thehydrogen gas during reaction was monitored. The results were presented as follows.

\1\\

\ I .~.\- --~-

't' IV \.- .._- - -

I!

\ III

II

-- _L -_. -II

I

II

.

I .I-,qv'1

--I----_+__ --

I ii !I I

20 \

1\.... \

II

time

Marks

(d) On the graph below, draw the curve to show how the concentration of hydrogen gas would 2vary during the reaction if a catalyst was used at 200°C.20_*~_~

j I

I I: i----.-J-...~.-.-.! !

Question 25

(a) Equilibrium was achieved fastest at 400°C. 9.4.2 H8, H13At this temperature, the concentration of hydrogen gas reached • Correct explanation and temperature.. 1-2a constant value in the least amount oftime.

The formation of ammonia is maximised when the finalconcentration of hydrogen gas is at a minimum.

This occurs at the lower temperature of the two, showing thatlower temperatures favour the formation of ammonia;therefore, the reaction is exothermic.

The catalyst is magnetite.

,[H2] ,i, --i

10 ==~A=$~l1time

The curve drawn by the students needs to show that the timetaken to reach equilibrium is less than the time taken on thegraph supplied in the question book for that temperature, butthe concentration of hydrogen gas at equilibrium is exactly thesame value as that on the graph supplied in the question bookfor that temperature.

Syllabus content, course outcomesand marking guide

9.4.2 H3, H7, H8, H13, Hl4• Correctly relates temperature to ammonia

formation , 1-2

9.4.2 H3, H8• Catalyst is magnetite or iron oxide . . . . . 1

9.4.2 H8, H13• Correct relationship between time and

[W] 1-2

• identify the reaction of hydrogen withnitrogen as exothermic

• explain why the rate of reaction isincreased by higher temperatures

• explain why the yield of product. inthe Haber process is reduced at hIghertemperatures using Le Chatelier'sprinciple

The graphs below show the fraction of ammonia present at equilibrium when nitrogen andhydrogen are reacted in a pressure vessel.

100

OJ..c 80~ --.S ~CIS'-'

•••.• OJc:: 1-103 60§ .§CIS

'+-< e0 ::s 40c:: .••.•0.E.....•.....•~ -u ....•CIS ::s1-1 0" 20~ OJ

(i) explain why the gas mixture'-is compressed during the industrial manufacture ofammonia. 1

(ii) Explain why only temperatures of 400-500°C are used in the manufacture ofammonia although a higher temperature would accelerate the reaction. 1

(c) Identify one reason for close monitoring of the gas stream entering the reaction vesselin the industrial synthesis of ammonia. 1

26. (a) N2(g) + 3H2(g) 7 2NH3(g) (l mk)(b) (i) As the forward reaction occurs with a decrease in the number of gas molecules, Le

Chatelier's principle states that increasing the pressure causes the equilibrium to moveto the right, increasing the yield of ammonia. (l mk)(ii)As shown in the graph (or predicted by Le Chatelier) a higher temperature wouldreduce the equilibrium yield of ammonia, so that the reaction is carried outat thelowest temperature which affords an acceptably fast reaction. (l mk)

(c) Anyone of: (l mk)To maintain the 3: 1 stoichiometric ratio of hydrogen:nitrogen, to prevent an excess ofeither in the chamber.To ensure no oxygen is present, to avoid explosion with hydrogen.To ensure no S compounds are'present, to avoid inactivating the catalyst.

(d) One of fertilisers, production of nitric acid, dyes, explosives, Solvay process etc (1 mk)

7. The fonnation of ammonia from its constituent elements can be summarised using the followingequation:

N2(g) + 3H2(g) ~ 2NH3(g)

The formation of ammonia is reduced when the reaction is conduc~ed under conditions of(A) high temperature and low pressure.(B) low temperature and high pressure.(C) high temperature and high pressure.(D) low temperature and low pressure.

Question 7 A 9.3.2,9.4.2The formation of ammonia is exothermic. and so its yield will increaseat lower temperatures. According to Le Chatelier's Principle, in thiscase the equilibrium will shift to the right as pressure is increased.

• explain why the Haber process is basedon a delicate balancing act involvingreaction energy, reaction rate andequilibrium

• explain that the use of a catalyst willlower the reaction temperaturerequired and identify the catalyst(s)used in the Haber process

• analyse the impact of increasedpressure on the system involved in theHaber process

• explain why monitoring of thereaction vessel used in the Haberprocess is crucial and discuss themonitoring' required

10. The production of ammonia needs raw materials. Which substance or process is the major source ofhydrogen?(A) Hydrogen carbonate ions(B) Distillation of liquefied air(C) Natural gas(D) Catalytic cracking

Question 10 C 9.4.2Hydrogen is produced by reacting methane with steam using a nickelcatalyst.

The graphs below show the fraction of ammonia present at equilibrium when nitrogen andhydrogen are reacted in a pressure vessel.

100

Q)...c:80.•..•........

.S ~C':l"'-'

.- Q)c:: '"'"o ~ 60E'XE OsC':l•.•... E0 ~ 41)c:: °C0.0...... ,.....•... -U .-C':l ~'"'" 0' 20

~ Q)

(i) explain why the gas mixture'-iscompressed during the industrial manufacture ofammonia. 1

(ii) Explain why only temperatures of 400-500°C are used in the manufacture ofammonia although a higher temperature would accelerate the reaction. 1

(c) Identify one reason for close,monitoring of the gas stream entering the reaction vesselin the industrial synthesis of ammonia. 1

The Haber Process is used in the synthesis of ammonia from gaseous hydrogen and nitrogen.The percentage conversion to ammonia at different temperatures and pressures is shown inthe table below.

Percentage conversion to ammonia at pressures indicatedTemperature °C 250atm 500 atm 1000 atm

150 94 97 99350 44 74 83550 12 28 34750 6 14 17

(d) Justify the use of high pressure and a temperature of 300-400 °C in the industrialsynthesis of ammonia. ' 2

26. (a) N2(g) + 3H2(g)-7 2NH3(g) 1(b) The data in the table show that increasing the temperature reduces the equilibrium

concentration of ammonia. forcing the equilibrium to the left. Hence the forward reactionis exothermic. 2

(c) Increasing pressure increases % ammonia yield. at all temperatures. This is confinned bythe stoichiometry of the reaction with 4 moles of gaseous reactants forming 2 moles ofgaseous products -hence an increase in pressure favours the side of fewer gaseous 2molecules.

(d) High pressure increases the equilibrium yield of ammonia. A temperature of 300-400deg. is a compromise to establish equilibrium quickly. and still obtain an acceptable yieldof ammonia. . 2

The table below shows the percentage yield of ammonia using the Haber process at apressure of 30 MPa.

Temperature (Kelvin) Percentage yield of ammonia200 94300 66400 44500 22600 9

(a) Use the table values to predict whether the production of ammonia is endothermic orexothermic. Justify your answer. . 2

29. (a) The production of ammonia is exothermic. This is shown by the yield which decreaseswith temperature. Le Chatelier's Principle shows that increased temperature s,hiftstheequilibrium to the left, absorbing heat energy and opposing the change. 2

(b) An increase in temperature will increase the speed of the reaction, but decrease the yield~~~ili~m. 1

(c) Increased pressure results in an increase in the rate of reaction, from increased reactantconcentrations. It also increases the yield as the reaction occurs with a reduction ofpressure (4 gaseous molecules ~ 2). By Le Chatelier's Principle an increase in pressureshifts the equilibrium to the right, towards reduced pressure. 2

• gather and processinformation from secondarysources to describe theconditions under which Haberdeveloped the industrialsynthesis of ammonia andevaluate its significance atthat time in world history

3. Manufacturedproducts,including food,drugs andhouseholdchemicals, areanalysed todetermine orensure theirchemicalcomposition

Chemistry Stage 6 Syllabus

Students learn to:

• deduce the ions present in a samplefrom the results of tests

• describe the use of atomic absorptionspectroscopy (AAS) in detectingconcentrations of metal ions insolutions and assess its impact onscientific understanding of the effectsof trace elements

• perform first-hal1dinvestigations to carry out arange of tests, induding flametests, to identify the followingIOns:

phosphatesulfatecarbonatechloridebariumcalciumleadcopperiron

• gather, process and presentinfonnation to describe andexplain evidence for the needto monitor levels of one ofthe above ions in substancesused in society

• identify data, plan, selectequipment and perform first-hand investigations to measurethe sulfate content of lawnfertiliser and explain thechemistry involved

• analyse information toevaluate the reliability of theresults of the aboveinvestigation and to proposesolutions to problemsencountered in the procedure

• gather, process and presentinformation to interpretsecondary data from AASmeasurements and evaluate theeffectiveness of this inpollution control

including food,drugs andhouseholdchemicals, areanalysed todetermine orensure theirchemicalcomposition

range of tests, including flame~ests, to identify the followingIOns:

phosphatesulfatecarbonatechloridebariumcalciumleadcopperIron

• gather, process and presentinfonnation to describe andexplain evidence for the needto monitor levels of one ofthe above ions in substancesused in society

A crystalline substance was tested to determine its composition. The following table summarises the testsperformed and their corresponding results.

TestTest Peiformed Resultnumber

1 physical appearance blue solid

2 colour of aqueous solution blue

3 colour of flame test green

4 reaction with sodium chloride no visible reactionsolution

7. Based on these results, which ion could be present in the crystalline substance?(A) Barium(B) Copper(C) Lead(D) Sodium

8. Which test is least likely to identify the positive ion present in this crystalline substance?(A) 1(B) 2

(C) 3(D) 4

Question 7 BThe presence of copper ions is possible due to the colour of thesubstance's solution and the colour produced by the flame test.

Question 8 DNo visible reaction with sodium chloride solution is a possible resuit fora range of different salt solutions.

Many common copper salts are blue or green in colour to produceaqueous solutions of similar colours. The flame lest for copper ionsproduces a green flame.

12. A student analysed a sample of water from an underground spring which was suspectedto be contaminated with certain metallic ions.

The student added dilute hydrochloric acid to the solution and noted no changes. Shethen added dilute ammonia to a second sample and also noted no change. She thenperformed a flame test and noted a faint but distinct red colour.

(A) Fe3+

(B) Ba2+

(C) Cu2+

(D) Ca2+

Dilute HCI is added and the white precipitate formed is filtered off.Na2S04(aq) is added to the filtrate but nothing happens.Addition of dilute NaOH results in the formation of a brown precipitate.

Which cations are present in the solution?(A) Ba2+ and Ca2+

(B) Ca2+ and Fe2+(C) Fe2+ and Cu2+(D) Pb2+and Fe3+

Question 11 D

PbCI2 and Fe(OHh are the solids formed.

i9.4.3

I

12. One technique that can be used to indicate the presence of some cations in solutions isflame testing. When a platinum wire loop is placed into a solution containing bariumions, the resulting flame colour is:

(A) yellow(B) scarlet(C) brick red(D) lime green

describe the use of atomic absorptionspectroscopy (AAS) in detectingconcentrations of metal ions insolutions and assess its impact onscientific understanding of the effectsof trace elements

• gather, process and presentinformation to interpretsecondary data from AASmeasurements and evaluate theeffectiveness of this inpollution control

14. The technique best suited to detecting low concentrations of metal ions in solutionswould be:

(A) fractional distillation(B) gas-liquid chromatography (GLC)(C) atomic absorption spectroscopy (AAS)(D) nuclear magnetic resonance spectroscopy (NMR)

13. Atomic absorption spectroscopy was developed in Australia in the 1950s by AlanWalsh while working at CSIRO. This technique works on the principle that:

(A) glass prisms can reflect wavelengths(B) electron beams bombard and ionise atoms(C) gaseous atoms absorb specific wavelengths of light(D) gaseous atoms give out specific wavelengths when excited

Railways often test the cooling water of their diesel engines for dissolved metals. The presence ofparticular metal ions in the water gives an indication as to the "health" of the engine. The mostcommonly used method for this analysis is atomic absorption spectroscopy.

In one particular analysis a chemist was testing for the presence of iron. She used a series ofstandard solutions to obtain the following results.

Concentration of Fe Absorbance(ppm) (%)

0 0.00

2 0.13

4 0.28

6 0.41

8 0.53

10 0.67

For each engine she placed 50 mL of sample in a 1000 mL standard flask. The flask was thenfilled to the mark with distilled, deionised water and shaken to ensure mixing. She then testedeach of the diluted samples and obtained the following results.

Engine NumberAbsorbance

(%)X12 0.04

X45 0.01

X67 0.30

(c) Suggest an hypothesis for the variation of iron concentration for the different engines.

Sample answer

Question 27

(a) H10• Correct graph. . . . . " 1

o 2 3 4 5 6 7 8 9 10 11Concentration of Fe (ppm)

Engine Absorbance Diluted [Fe] Sample [Fe]number (%) (ppm) (ppm) .~

Xl2 0.04 0.6 20x 0.6 = 12

X45 0.01 0.1 20 x 0.1 = 2

X67 0.30 4.5 20 x 4.5 = 90

H10• Correct sample value, i.e. multiplying by the

dilution factor " 2

The first two engines are showing little dissolved iron and assuch have no problems but the third has a significant amountprobably due to lUsting of iron components in the engine.

H14• Feasible hypothesis for all engines ..... 2

A food company developed a new breakfast chocolate drink containing iron which isessential to human health.

The graph below shows the absorbance of a number of standard solutions containing ironusing an Atomic Absorption Spectrometer.

··..T···j· ..·l....r..·r..l..···I,· .... r ..r·r..T··r·l· ..r··r···f,....r'T"'r"r..·····.•·..···.,·······,._···!· ..···.•···..··t······ .•_ ..··I•••••••I·······l_ .._.t ••••··~·······I·······r·..··..•·•.····I..··- •.·_•.·•····· ..i··•••••;.··.

I I I I I I I ! I I ! I t ,.j I i I I i Io .~0 ..··t··_···,····· ..I·······f······~·······I·····-~······, i--•••••f···· ..,t..····-:..·..··I.......•.........•......·I· ··;.···..··i.•.•···i•.•..•.t .I I I Ii! I ! ! i I I I " I I Ii! I

j +ttl+t1l+~H-T:·ltH·5l o·M t-l-+J-rtTt-i+~+·'-·Tt-J-;-it~ il~-·+it+- -I n+ l-r-H-+-I-

0·/0 1-1-.- - -I- i-l--tl-f-'T!-h+'·.+1. r-,--,-IT!-,lti+ -liltt

o I :2. '3 '4-

A 10.0 mL sample of the chocolate drink was diluted to 50.0 mL and placed into thespectrometer. It was found to have an absorbance of 0.190.

(a) What is the concentration of iron, in ppm, in the undiluted chocolate drink?

(b) What mass of iron would you consume by drinking a 260 mL (260 g) glass of thechocolate drink? 1

(c) The recommended daily allowance of iron for people over 12 years of age is 18 mg.What percent of your daily needs does a 260 mL glass of the chocolate drink provide? 1

29. (a) [Fe] = 2.6 x 50/10 = 13 ppm(b) Mass of Fe in 260 g = 13 x 260 X 10-6 = 3.38 mg(c) % daily allowance = 3.38 x 100/18 = 18.8%(d) The undiluted drink has a concentration beyond the calibration scale for the

spectrometer used.

(1 mk)(1 mk)(1 mk)

(1 mk)

Atomic absorption spectroscopy (AAS) is a method used to determine the concentration of ametal ion down to levels of ppm or ppb. Samples of accurately known concentration are vaporisedand allowed to absorb radiation of a specific frequency. The amount of radiation absorbed is ameasure of how much of the ion is present.

lens monochromator detector

tp--GO--l!}--~6-TcIDhollow atomized amplifier readout

cathode lamp sample

Concentration of cadmium (ppm) 2.1 3.9 6.0 7.9 9.8

Absorbance 0.16 0.32 0.49 0.64 0.80

A sample of soil containing cadmium was dissolved and diluted by a factor of 100. 3Its absorbency was measured and found to be 0.53.

Graph the calibration data given in the table and use your graph to calculate the concentration ofcadmium in the soil sample.

_ •• h_ •• ' ._-. _._- -_. ..__ ... R ___ - '_R_" --- -- ._-~ ._- - _._. --- -- ---

..._-- _.-, -- f-_._ .. -- - - "- .-_ ..- --- ._- _._M' --·1- -- ---- ----

0.0oconcentration of cadmium (ppm)

From the graph, concentration is 6.6 ppm, so sample of soil contains6.6 x 100 = 660 ppm.

Syllabus content, course outCOlllesand marking guide

9.4.3 H6, Hl3• Graph with correctly labelled axis,and

appropriate scale'AND• Concentration read correctly from graph,

correct answer , . . . . 3

Graph with correctly labelled axis, andappropriate scale

AND• Concentration read correctly from graph. 2

• Graph with correctly labelled axis, andappropriate scale

OR• Concentration read correctly from graph. 1

A sample of river water was analysed for nickel using Atomic Absorption Spectroscopy(AAS).A 25mL sample was diluted to 250mL with distilled water, and measured with the AASinstrument. An average absorbance reading of 0.350 was obtained, for the diluted sample.The results for a set of nickel standards is included in the table below.

Standard nickel concentration Absorbanceg.mL-1

2.0 x loot> 0.1344.0 x loot> 0.2726.0 x loot> 0.416

I

I

I

I I

i

I

,

I I I, , I

II I, i

(b) Using the graph, determine the concentration of nickel in the original sample of riverwater. 2

(b). From the calibration curve [Ni2+] = 5.1 X 10-6 g mL-1

Concentration in water sample = 5.1 x 10.5 g mL-1

• identify data, plan, selectequipment and perform first-hand investigations to measurethe sulfate content of lawnfertiliser and explain thechemistry involved

• analyse information toevaluate the reliability of theresults of the aboveinvestigation and to proposesolutions to problemsencountered in the procedure

As part of the ~ourse you designed and carried out a first hand investigation to determine thepercentage of sulfate ion in a lawn fertiliser. Read the following two methods. In each case,barium sulfate is produced.

STUDENT A"I dissolved a 10 g sample of ammonium sulfate in a total volume of 100 mL of solution, added10 mL of dilute hydrochloric acid and an excess of 0.1 M barium chloride solutiori. The whiteprecipitate formed was collected and 5.4 g of precipitate was present. I noticed that some solidpassed through the filter paper."

STUDENTB"I dissolved a 2 g sample of Epsom salts (MgS04) which I had bought from the garden shop, tomake up 30 mL of solution. Some dilute acid was added as were a few drops of Alizarin Redindicator. Barium chloride solution (0.2 mol L-1) was added from a burette until the indicatorchanged from a pale yellow to a pale red, indicating the end point The volume added was44 mL."

Evaluate each of the methods used in terms of procedure and validity of results.Determine the percentage of sulfate in the Epsom salts.

Question 26

Student A has performed a gravimetric analysis. Adding dilute acidallows hydroxide and carbonate ions to be removed as water andcarbon dioxide gas. Adding excess barium chloride ensures all thesulfate ions are precipitated, so the method so far is very good. Thefiltration resulted in the loss of some precipitate, which means theresults will be inaccurate and hence invalid. The student needs to refine 1-----------------the method to ensure all the BaS04 is collected. Student B has used • Some evaluation shown or comment onvolumetric analysis. Errors in the method relate to accuracy of validity of resultsmeasurements in weighing, volume readings and detecting the end ANDpoint. Repetition is required to eliminate random errors and produce • Correct calculation with method andmore valid results. units , 4-5

1I(S042-) in fertiliser sample = n(BaCI2) added from burette.

n(BaCI2) = c V

2-:.n(S04 ) = 0.2 x 0.044 = 0.0088

2-m(S04 ) =n xM

= 0.0088 x 96 = 0.845 g2- 0.845%(S04 ) = -2- x 100 = 42%

9.4.3 H3, H8, HlO, Hll, H12.H13, H14• Evaluates each method for procedure

and comments on validity of results• Correct calculation with method and

units 6-7

• Some evaluation shown or comment onvalidity of results

AND• Correct answer and no method 2-3

• Some evaluation shown or comment onvalidity of results

OR• Correct answer and no method .

(A) acid/base titration(B) atomic absorption spectroscopy(C) pH measurement(D) gravimetric analysis of a precipitate

15. A 1.0 g sample offerti1iser was dissolved in water and excess barium chloride was added to precipitate1.6 g of white barium sulfate. The percentage mass of sulfate in the fertiliser is

(A) 89%

(B) 66%

(C) 22%(D) 41%

Question 15 B

mol (BaS04) = ~ = 0.007233

mol (S04)2- = 0.007

m(S04)2- = 0.007 x 96

% = 0.66 x 1001

=66%

! 9.4.3I

(a) Identify the steps you followed in performing a first hand investigation to measure thesulfate content oflawn fertiliser. 3

(b) Describe how you calculated the percentage of sulfate in the fertiliser includingrelevant equations in your answer.

25(a) A quantity of lawn fertiliser was ground up in a mortar and pestleSet quantity weighed out eg 2.00 g and dissolved in dilute HCI and stirred.Excess BaCh was then added to the solution to precipitate the BaS04The precipitate of BaS04 was filtered dried and weighed ..

(b) Initial mass of ground lawn food weighed out eg 2.00 g.The mass of sol- was detem1ined in the BaS04Mass of soi- in sample = (reI mass of S042- / reI mass of BaS04 ) x 2gThen the % of sol- in lawn food = (Mass of sol-/ 2g) x 100

4. Human activityhas causedchanges in thecomposition andthe structure ofthe atmosphere.Chemistsmonitor thesechanges so thatfurther damagecan be limited

• describe the composition and layeredstructure of the atmosphere

• identify the main pollutants found inthe lower atmosphere and theirsources

• describe ozone as a molecule able toact both as an upper atmosphere UVradiation shield and a loweratmosphere pollutant

• describe the formation of acoordinate covalent bond

• demonstrate the formation ofcoordinate covalent bonds using Lewiselectron dot structures

• compare the properties of the oxygenallotropes 02 and 03 and account forthem on the basis of molecularstructure and bonding

• compare the properties of the gaseousforms of oxygen and the oxygen freeradical

• identify the origins ofchlorofluorocarbons (CFCs) andhalons in the atmosphere

• identify and name examples ofisomers (excluding geometrical andoptical) of haloalkanes up to eightcarbon atoms

• discuss the problems associated withthe use of CFCs and assess theeffectiveness of steps taken toalleviate these problems

• analyse the information available thatindicates changes in atmosphericozone concentrations, describe thechanges observed and explain howthis information was obtained

Students:

• present infom1ation fromsecondary sources to write theequations to show thereactions involving CFCs andozone to demonstrate theremoval of ozone from theatmosphere

• gather, process and presentinformation from secondarysources including simulations,molecular model kits orpictorial representations tomodel isomers of haloalkanes

• present information fromsecondary sources to identifyalternative chemicals used toreplace CFCs and evaluate theeffectiveness of their use as areplacement for CFCs

4. Human activityhas causedchanges in thecomposition andthe structure ofthe atmosphere.Chemistsmonitor thesechanges so thatfurther damagecan be limited

• describe the composition and layeredstructure of the atmosphere

• identify the main pollutants found inthe lower atmosphere and theirsources

describe ozone as a molecule able toact both as an upper atmosphere UVradiation shield and a loweratmosphere pollutant

Read the following statements.

I Water vapour and carbon dioxide are both greenhouse gases.II To reduce ozone depletion chlorofluorocarbons have been replaced by halons such

as 1,2-dibromoethane.III Ozone is a pollutant in the stratosphere but acts as a UV absorber in the troposphere.

Which of the statements I, II and III are true?(A) I only(B) I and II only(C) I, II and III(D) II only

Question 12 A 9.4.4

Halons are also ozone-depleting gases; in statement III, stratosphereand troposphere should be interchanged.

describe the fOIDlation of acoordinate covalent bond

demonstrate the formation ofcoordinate covalent bonds using Lewiselectron dot structures

compare the properties of the oxygenallotropes 02 and 03 and account forthem on the basis of molecularstructure and bonding

compare the properties of the gaseousforms of oxygen and the oxygen freeradical

11. Which of the following exhibits coordinate covalent bonding?

(A) oxygen molecule(B) hydronium ion(C) ammonia(D) ethanol

The allotropes of oxygen, 02 and °3,are both common in the Earth's atmosphere. However, theyare found in different layers of the atmosphere.

(c) With the use of Lewis electron dot structures, show how the shapes of ozone and oxygen 2are different.

Oxygen is sparingly soluble in water. ExpLain why ozone is considerably more soluble inwater.

Question 20

(a) Troposphere. • Identifies the troposphere as the layer in theatmosphere in which oxygen is mostabundant. " . . . .. . . .. I

• Identifies the stratosphere as the layer in theatmosphere in which ozone is mostabundant. . . . . . . . . . . . . . . . . . . . .. . . .. I

• Provides correct Lewis dot structure for bothozone and oxygen

• Provides correct Lewis dot structure foreither·ozone or oxygent .

The Lewis electron dot structure for oxygen is

-D···0··e •• •• •

••.0..eti·· ·0:

•• •••

Syllabus content, course outcomes andmarking guide

Identifies that ozone is polar and oxygen isnon-polarIdentifies that polarity of ozone createsattraction with polar water moleculesIdentifies that oxygen is only attracted towater due to weak dispersion forces . . .. 3

Ozone and water are both polar molecules while oxygen is non- i •polar. Therefore the attraction between ozone and water is i

!

greater due to dipole-dipole interactions. Oxygen is only i.

attracted to water by weak dispersion forces. This results in agreater relative solubility between ozone and water whencontrasted with oxygen in water.

i· Identifies that ozone is polar and oxygen isnon-polar

, • Identifies that polarity of ozone createsattraction with polar water molecules ... 2

!. Identifies that ozone is polar and oxygen isnon-polar. . . . . . . . . . . . . . . . . . . . . . . .. I

14. Select the molecule from below that possesses a coordinate covalent bond.

(A) carbon dioxide(B) water(C) ozone(D) oxygen

H +H:N:H..

H

(b) A coordinate covalent bond is one where the shared electron pair is provided by one of thebonded atoms. The ammonium ion forms when the unshared pair of electrons on thenitrogen atom in ammonia, is used to fom1 a bond with a proton. 2

• identify the origins ofchlorofluorocarbons (CFCs) andhalons in the atmosphere

present information fromsecon.dary sources to write theequations to show thereactions involving CFCs andozone to demonstrate theremoval of Ozone from theatmosphere

12. Identify the compound in the atmosphere which reacts with chlorofluorocarbons(CFC's). '

(A) water(B) carbon monoxide(C) ozone(D) carbon dioxide

• identify and name examples ofisomers(excludinggeometricalandoptical) of haloalkanes up to eightcarbon atoms

• gather, process and presentinformation from secondarysources including simulations,molecular model kits orpictorial representations tomodel isomers of haloalkanes

• present information fromsecondary sources to identifyalternative chemicals used toreplace CFCs and evaluate theeffectiveness of their use as areplacement for CFCs

F ClI IH-C-C-ClI IF Cl

(A) 1,1,2,2,2 - difluorotrichloroethane(B) ethane - 1,1 - difluoride - 2,2,2 - trichloride(C) 1,1,1 - trichloro - 2,2 - difluoroethane(D) trichlorodifluoroethane

13. Whichof the followingpairsare NOTisomers?(A) F H H H H F H

I I I I I I IH-C-C-C-C-H H-C-C-C-F

I I I I I I IH F H H H HH-C-H

IH

(B) F H Cl H CI H F HI I I I I I I I

H-C-C-C-C-H H-C-C-C-C-H

k k I k k k I hH-C-H H-C-H

I IH H

(C) F H CII I I

H-C-C-C-HI I IH H F

(D) CI H CII I I

H-C-C-C-HI I I

H H Cl

F H HI I I

H-C-C-C-HI I I

Cl H F

H H HI I I

H-C-C-C-HI I I

Cl Cl Cl

CI FI I

CI-C-C-FI I

CI F

(A) 1,1,1 ,2,2,2-chlorofluoroethane(B) 1,1, I-trifluoro - 2,2,2-trichloromethane(C) 1,1,1 ,2,2,2-chlorofluoromethane(D) 1,1, I-trichloro - 2,2,2-trifluoroethane

• dISCUSS tile prOblems assoclatea Wlln

the use of CFCs and assess theeffectiveness of steps taken toalleviate these problems

• analyse the information avai lable thatindicates changes in atmosphericozone concentrations, describe thechanges observed and explain howthis information was obtained

Syllabus content, course outcomes andmarking guide

Question 27 \9.4.4 HI,H4,HI3,H]4,Chlorofluorocarbons (or CFCs) are carbon compounds that contain '. Demonstrated ability to:chlorine and fluorine, e.g. CF3Cl. CFCs were developed to replace i· Define CFCs and identify at least oneammonia as a refrigerant because they were thought to be less harmful.! example;They were also used as solvents, propellants and blowing agents in i • Identify and describe problems associatedfoams because they were viewed as inert. with the use of CFCs;CFC gases were released to the atmosphere while being used in these i· Explain the need to develop alternatives;commercial applications. While they did not react in the troposphere, i· Identify and describe alternatives;when they make their way to the stratosphere the UV energy present I· Assess effectiveness of. alternatives;breaks C-CI bonds, releasing Cl free radicals. Chlorine and other free! • Includes relevant equatIOns 7radicals like bromine from halons deplete the ozone layer according to :-·····--·0---·----·-----· ..·-·-····..- ..-·····---·..···-··....·---..·__·_-··--_..···.._·-d-:----the following equations: ~ i • Of~monstrated knowledge and understan mg

CF3Cl -t CF3 + CI : • A definition of CFCs and at least oneCI +03 -t CIa + O2 example;cIa + a -t CI + 0, i • Problems associated with the use of CFCs;

~ I

The continual generation of the chlorine radical means that the damage i • The need to develop alternatives;caused by CFCs could last for 150 years. The depletion of the ozone !. The type of alternatives available;layer allows more UV radiation to reach Earth, which increases the ! • Assess effectiveness of alternatives ... 5-6chances of cancer in living things (including humans). It also creates an r. -----Demonstrated knowledge and understandingincrease in the enhanced greenhouse effect. The enhanced greenhouse! of:effect is caused by greenhouse gases absorbing heat rays that come , • A definition of CFCs;from the Earth's surface and emitting them back to the Earth's sutface, i • Problems associated with the use of CFCs;raising the temperature of the atmosphere. i. The need to develop alternatives;There have been two main steps taken to reduce the breakdown of AND/ORozone in the stratosphere. These are: : • The type of alternatives available .... 3-4

The Montreal Protocol, a treaty to achieve global control \---_.._- ..----_..------_.--- ..----------.-.- ..----------.of production and use of CFCs. Global commitment to 1. Demonstrated knov;']edge of:the reduction of the production and use of CFCs and . A definition of CFCs;halons is needed. Poorer countries ",till need assistance :. Problems associated \\lith the use of CFCs;to achieve targets and if industrialised nations AND/OR00vernments do nOl sjo-n and adhere to the Protocol i. The need to develop alternatives.CFC levels will not be~educed and the ozone layer ~ill AND/ORcontinue to be damaged_ At present, although most '. The type of alternatives available .... ]-2countries have signed the Protocol, Australia and theUntied States have not. Both nations, however. havephased out CFCs and halons. China is thought to be stillproducing significant amounts of both substances andconsequently the effectiveness of the Montreal Protocolas a global management system is reduced.

The identification and introduction ot alternativechemicals, such as hydrochlorofluorocarhons (HCFCs)and hydrofluorocarbons (HFCs).The effectiveness ofthese compounds has been mixed. Although HCFCscontain hydrogen atoms and fewer chlorine atoms theycan still undergo reactions with OH free radicals in thetroposphere. This reaction is slow, but HCFCs will stillreach the stratosphere and produce chlorine radicals.HFCs, which contain no chlorine, promise to be moreeffective. They react readily with OH in the tropospherebut because they do not contain chlorine, undesirableradicals should not be produced.

5. Human activityalso impacts onwaterways.Chemicalmonitoring andmanagementassists inproviding safewater for humanuse and toprotect thehabitats of otherorganisms

• identify that water quality can bedetermined by considering:- concentrations of common ions

total dissolved solidshardnessturbidityaciditydissolved oxygen and biochemicaloxygen demand

• identify factors that affect theconcentrations of a range of ions insolution in natural bodies of watersuch as rivers and oceans

describe and assess the effectiveness ofmethods used to purify and sanitisemass water supplies

• perform first-handinvestigations to usequalitative and quantitativetests to analyse and comparethe quality of water samples

• gather, process and presentinformation on the range andchemistry of the tests used to:

identify heavy metalpollution of water

- monitor possibleeutrophication ofwaterways

• gather, process and presentinformation on the features ofthe local town water supply interms of:- catchment area- possible sources of

contamination in thiscatchment

- chemical tests available todetermine levels and typesof contaminants

- physical and chemicalprocesses used to purifywater

- chemical additives in thewater and the reasons forthe presence of theseadditives

describe the design and composition ofmicroscopic membrane filters andexplain how they purify contaminatedwater

5. Human activityalso impacts onwaterways.Chemicalmonitoring andmanagementassists inproviding safewater for humanuse and toprotect thehabitats of otherorganisms

• identify that water quality can bedetermined by considering:_ concentrations of common ions- total dissolved solids- hardness- turbidity- acidity- dissolved oxygen and biochemical

oxygen demand

• perform first-handinvestigations to usequalitative and quantitativetests to analyse and comparethe quality of water samples

Decomposition products

Element from By aerobic By anaerobicorganic material processes processes

carbon carbon dioxide methane

nitrogen nitrate ammonia

sulfur sulfate hydrogen sulfide

Stagnant (non-flowing) water tends to produce a strong odour while moving water does not. Which ofthe following best explains this?(A) Water which flows mixes readily with oxygen, decreasing the solubility of anaerobically

produced gases and so releasing these gases into the atmosphere.(B) Water which flows mixes readily with oxygen, increasing the solubility of anaerobically

produced gases keeping them in the water and so reducing odour.(C) The aerobic processes of stagnant water produces strong smelling compounds.(D) Oxygenation of water is promoted by the mixing of moving water with air, thus increasing the

opportunity for aerobic decomposition.

Question 6 DAs water flows, it mixes with air from the atmosphere. This allowsoxygen to mix with the water and so increases the dissolved oxygencontent of the water. The increased available oxygen in the water makes iaerobic decomposition possible. \

11. A chemist was asked to analyse a supply of drinking water for the presence of common ions andhardness. The most common ion in drinking water is chloride. Identify the test that would allow thechemist to detect the concentration of chloride ions present.(A) A flame test.(B) Addition of AgN03.

(C) Titration with AgN03.

(D) Atomic absorption spectroscopy.

Question 11 CConcentration is a quantity. therefore titration is the best method.

15. The following table shows the potential release of acid into waterways from someminerals as a result of mining.

Potential acid release from some alunite group mineralsMineral Formula moles H+/mole

Plumbojarosite PbFe6(S04)4(OH) 12 6Benverite Pb(Cu,Fe,Alh(S04)z( OH)6 0-5

Natrojarosite NaFe3(S04)z(OH)6 . 3Alunite KA1](S04)z(OH)6 0

The most noticeable effect of run off from a mine waste heap with a high concentrationof plurnbojarosite into a nearby stream would be:,

(A) a rapid rise in BOD levels(B) pH levels would drop(C) dissolved oxygen levels would drop(D) eutrophication would begin ._

15. Students at a coastal school were given some water samples to analyse. Their results are shown in thetable below.

Test Turbidity Nitrate concentration Dissolved oxygen

Sample 1 very low low 9ppm

Sample 2 very low low 4ppm

Sample 3 medium high 1ppm

Sample 4 high low 3ppm

(A)

(B)

(C)(D)

Source

Flowing river Downstream from a diary farm

Sample 1 Sample 4

Sample 1 Sample 3

Sample 2 Sample 3

Sample 2 Sample 4

Question 15 B 19.4.5

Rowing water will have the most dissolved oxygen. Runoff from the 1dairy farm will provide nutrients for organisms from increased nitrate. Iand lowering DO. !

4. \Vater hardness is used to describe water that contains significant amounts of specificions. Hard water will not lather easily with soaps. These ions are: .

(A) Na + and cr ions(B) NH4+ and OH- ionsC) ")+ d Pb")+'( Hg- an. - IOns

(D) Mg2+ and Ca2+ ions

(b) Describe how you could quickly tell if a sample of water came from Sydney or BrokenHill.' 2

27. (a) The presence of a relatively high concentration of calcium and/or magnesium ions. 1(b) Either test the lathering qualities of the water with soap, which will form a non-lathering

scum (precipitate) with hard water, or add carbonate ions, which form a white ppte. ofCaC03 with Ca2+ ion. 2

12. To test for water hardness the chemist should test for the presence of(A) calcium and carbonate ions.(B) calcium and magnesium ions.(C) carbonate and phosphate ions.(0) phosphate and sulfate ions.

Question 12 BMg:!+ and Ca:!+ are associated with hard water.

26. (a) Anyone of pH, turbidity, TDS, oxygen level, BOD etc 1(b) eg., High BOD. With a high BOD the oxygen demand from organic material in the water

results in reduced oxygen levels, and the death of aerobic organisms including animals.The growth ofanerobic bacteria is promoted, resulting in release of acidic/toxiccompounds such as hydrogen sulfide.

chemistry of the tests used to:- identify heavy metal

pollution of water- monitor possible

eutrophication ofwaterways

The successful growth of oysters is highly dependent on the quality of the water in which they arefaimed. The following parameters need to be monitored to ensure water quality is maintained.

Parameter

Minimum dissolved oxygen (ppm) 9.5

Maximum biochemical oxygen demand (ppm) 1.5

Maximum colifOlm (toxic) bacteria (number per 100mL) 5

Maximum temperature (0C) '" 16

pH range 6.5-8.5

Maximum turbidity (NTU) 4

Parameter

Dissolved oxygen (ppm) 6.5

Coliform bacteria (number per 100 mL) 9500

Temperature (0C) 19

pH 4.3

Turbidity (NTU) 10

(b) Predict the effect of the bacteria count on the biochemical oxygen demand in this river. 2Justify your answer.

Question 25

(a) There is a relatively high number of coliform bacteria in thewater sample from the river. This large number of bacteriawould require a large amount of oxygen and so a decreasedamount of oxygen would be present in the water.

H8, H13Links low dissolved oxygen to high bacteriacount AND therefore high demandfor oxygen 2

States low dissolved oxygen due tohigh bacteria count

ORStates a high demand for oxygen. . . . . .. I

The high number of coliform bacteria require a large amount of H8, HI3oxygen, therefore the biochemical oxygen demand is relatively • Predicts biochemical oxygen demand willhigh. The demand will continue to increase as the bacteria be high (and increase) AND that otherreproduce. organisms will suffer 2

As a result, other organisms will die. There is also a possibilityof eutrophication. Predicts biochemical oxygen demand will

be highOR

Predicts other organisms will suffer .....

Based on the values shown, this river would not provide anappropriate environment to grow oysters. The amount ofoxygen is too low because the bacterial levels are too high.Also, these bacteria are toxic and so could infect the oysters;this could increase the risk of food poisoning.

H8, H13States that river is unsuitable for growingoysters with justification . . . . . . . . . . . . . 2

States that river is unsuitable for growingoysters . . . . . . . . . . . . . . . . . . . . . . . . . .. I

flow~

River A~

(i) dissolved oxygen.

(ii) phosphate ions.

(iii) lead ions.

Complete the table, and compare and account for the relative values of each of theseconcentrations.

Concentration in River ASubstance relative to River B Explanation

(higherllower/same)

Dissolved oxygen

.-

Phosphate ion

Lead ion

Question 26

Concentration inConcentration River A relative Explanation

to River B .--

No eutrophication

Dissolved 02 higher indicates lower oxygenrequirement by aquaticorganisms.

Lack of phosphate wouldPhosphate ion lower decrease the probability

of eutrophication.

The presence of lead ionsLead ion same would have no effect on

eutrophication.

H8• Correctly predicts relative concentrations

AND accounts for relative values .. , . . . 4

• Correctly predicts relative concentrationsAND accounts for relative values of eitheroxygen or phosphate , . . . 3

• Predicts some relative concentrations ANDpartially accounts for relative values .... 2

; • Identifies any two other factors used todetermine water quality. . . . . . . . . . . . .. 2

t·~_·..···__ ··_·~_··~··_·..··_-_··_·_-_·_·__·_·_·__···_-_ __._ -_.._ _ _ __.__ _ .I. Identifies any factor used to determine \J.'ater

quality . . . . . . . . . . . . . . . . . . . . . . . . . .. I

Two of the fo]]o\\ling lists: :- Any two factors 2pH is affected by natural factors such as minerals in the water, i~·..·-A--·--···..·_··f··---··__·_--_· __ ·__·__·····..···-'--""""'''''-''''''i''dust in the air, acid rain and photosynthesis, as well as human! ny one actor .activities, such as overloading of nutrients from farms or sewage:causing algal blooms, industrialisation leading to greater thannormal levels of acid rain due to increased oxides of carbon,sulfur and nitrogen in the air, and mining.

Water bodies are tested regularly using a pH meter and are in ••danger of becoming polluted when the range of pH valueschanges too much. Indicators of polluted water would include ,._-_ __ _._..-..- - - --_ _ _ _ __._ _._.-__ .changes in aquatic life. •• Some knowledge of pH and water

quality _. . . . . .. I

Question 21

(a)

! 9.4.5

Relates pH to water pollution and gives onemonitoring method 2

A student analysed a 2.85 gram sample of washing powder for its phosphorus content. Thephosphorus was precipitated as Mg2P207 and then filtered. The mass of the precipitate was0.125 gram.

(a) To assure accuracy describe TWO procedures that the student needed to undertake after- filtration and before determining the mass of the precipitate. 2

(c) Phosphorus in detergents in the form of phosphates acts as low cost builders, buttogether with nitrates cause pollution in waterways through the process ofeutrophication.

Wash the precipitate with distilled waterDry the precipitateMoles of ppte. = 0.125/mol. mass = 0.125/222.56 = 5.62 x 10-4Moles of P present = 2 x moles ppte=1.123 x 10-3 mol% P in detergent = 1.123 x 30.97 x 100/2.85 = 1.22% (1-mk)

(c) Excess nutrients such as nitrates and phosphates can cause excessive growth of algaeand other organisms in waterways.(l mk) One type of alga that may grow excessivelyis blue/green algae which is toxic to livestock and can affect humans. The algal growthblocks the entry of sunlight, and increases BOD (1 mk) creating an anoxicenvironment leading to death of aquatic organisms.(lmk)

(1 mk)(1 mk)

In May 2003, heavy rains swept through the Sydney region. Describe a possible effect on each ofthe following factors that determine water quality of local waterways.

Turbidity will increase as more undissolved solids enter thewaterway and become suspended.Total dissolved solids will increase due to runoff.Nitrogen:phosphorus ratio will increase as sewage and gardenrunoff adds nutrients. f--C--t-d--· -t·--f-2-ffj-t-----2-• orrec escnp IOn0 e ec s .pH will probably be unaffected or slightly lower since rain isslightly acidic.

9.4.5 H4, H8, H14• Correct description of each effect . . . . . . 4

• identify factors that affect theconcentrations of a range of ions insolution in natural bodies of watersuch as rivers and oceans

• describe and assess the effectiveness ofmethods used to purify and sanitisemass water supplies

• describe the design and composition ofmicroscopic membrane filters andexplain how they purify contaminatedwater

15. Following the contamination of water supplies in Sydney in 1998 with Cryptosporidium and Giardia,many residents now use membrane filters in their homes. The technology these filters use is based onwhich of the following assumptions?(A) Water flows through the membrane, leaving dissolved substances behind.(B) Cryptosporidium and Giardia are microorganisms and the filter pores are very small.(C) Water can be forced to move through a membrane from low ion concentrations to high ionic

concentration leaving contaminants behind.(D) All of the above.

Question 15 BMembrane filters have pores smaller than microorganisms. C is a true istatement, but is not the reason why microorganisms are removed. j

treateddischarge

activatedsludge

skimming+

sedimentation

tricklingfilters anaerobic

respirationanaerobicrespiration

BODremoval

(A) adjust the pH(B) improve the BOD levels(C) kill pathogens(D) activate enzymes necessary for sewage digestion

14. Why are microscopic membrane filters useful?(A) They are unable to remove colloidal particles.(B) Organisms such as Giardia and Cryptosporidium will not pass through them if the pores are

small enough.(C) Osmosis can be used to produce drinking quality water.(D) They are cheaper than chemical treatments.

19.4.5

The table below gives the concentration in parts per million, of some substances found inSydney's tap water, along with the National Health and Medical Research Council (NHMRC)guidelines for maximum safe concentrations of these substances.

Substances Concentration in ppm NHMRC guidelinesin Sydney tap water concentration ppm

Total dissolved solids 86 1000Calcium ion 15 200Chloride ion 19 400Nitrate ion 0.4 12

(c) Identify one other substance which can affect water quality, and describe an adverseeffect if this substance is at too high a concentration. 2

(d) Sydney tap water has chlorine added in varying concentrations. Discuss the purpose ofadding this chlorine. 2

-25 (a) Add a few drops of dilute silver nitrate solution. If chloride ion is present a white ppte. of

AgCI forms. 1(b) Nitrate ion may come from run-off from gardens and farms that have had nitrate fertiliser

applied. 1(c) eg., sodium ion, which causes health problems in drinking water, including increasing

blood pressure and the risks of circulatory diseases. 2(d) The chlorine acts as a disinfectant by destroying bacteria and other microbes, including

those which can cause diseases such as cholera, typhoid and dysentery. 2

• gather, process and presentinformation on the features ofthe local town water supply interms of:- catchment area- possible sources of

contamination in thiscatchment

- chemical tests available todetem1ine levels and typesof contaminants

- physical and chemicalprocesses used to purifywater

- chemical additives in thewater and the reasons forthe presence of theseadditives

(A) acidity(B) hardness(C) phosphate concentration(D) temperature