CHEMICAL MONITORING

AND MANAGEMENT

AIR

OZONE

WATER

WASTE WATER

HUMAN USE

OTHER POLLUTANTS

POLLUTANT

PROTECTANT

CFCs

IDENTIFYING IONS

SULFATE AAS

COMBUSTION

HABER PROCESS

CHEMICAL MONITORING AND MANAGEMENT

2

SUBSECTION 1Much of the work of chemists involves

monitoring the reactants an products of reactions and managing reaction conditions

Subsection 1 1.2.1 & 1.3.1

* specific chemical occupation named industry branch of chemistry e.g. analytical chemistry explain a chemical principle that the chemist

uses • GC/GLC – adsorption, solubility (text example)

1.2.2 collaboration between chemists – Text p. 198, 199

4

1.2.3 monitoring combustion

*m

onit

or

em

issi

ons

from

com

bu

stio

n

react

ion

s in

ord

er

to e

nsu

re m

inim

um

am

oun

ts o

f to

xic

mate

rials

rele

ase

d

into

en

vir

onm

ent

in

com

plet

e co

mbu

stio

n –

CO

su

lfur

com

poun

ds in

coa

l & c

rude

oil

– S

O2

hi

gh te

mp

in in

tern

al c

ombu

stio

n en

gine

s –

NO

, N

O2

pa

rtic

ulat

es –

som

e of

whi

ch c

ome

from

co

mbu

stio

n

5

Subsection 2Chemical processes in industry

require monitoring and management to maximise

production

7

NitrogenAmino Acids

R OH N C C O H H

Nucleic Acids

8

THE HABER PROCESS

The reaction of N2 gas with H2 gas to form NH3 that eventually comes to EQUILIBRIUM in a CLOSED SYSTEM. Under normal conditions of T and P reaction proceeds very SLOWLY and the position of equilibrium is far to the LEFT.N2(g) + 3H2(g) 2NH3 H = -92kJ

bp -196oC bp -253oC bp -33oC

9

THE HABER PROCESS

RAW MATERIALS* air nitrogen

Fractional distillation of air

* natural gas hydrogen From methane gas reacted with steam

CH4(g)  +  2H2O(g)     CO2(g)  +   4H2(g)

10

THE PRODUCTION OF AMMONIA

* manufacture of the reactant gases, N2, H2

* purification* compression

* catalytic reaction to form NH3

* recovery of the NH3

* recycling of unreacted N2 and H2

THE SIX MAIN STEPS

11

THE HABER PROCESSThe conflict between rate and extent of

reaction (yield) – three key aspects need to be considered in choosing the conditions

* the yield – how far the reaction goes (how much NH3)

* the rate – how fast the ammonia is formed

* the energy account – how much energy can be saved/obtained

12

THE HABER PROCESSThe compromise between

temperature, pressure and yield of ammonia within the extreme positions of:

* a high yield but low rate of reaction at low temperatures (e. g. 25oC)

* a low yield but high rate of reaction at high temperatures (1000oC)

* is achieved by using A CATALYST its role is to permit a reduction in the operating

temperature in the converter

THE HABER PROCESS* Catalyst lowers the activation

energy so that the N2 bonds and H2 bonds can be more readily broken

* At these lower temperatures, the reduced Ea via the catalyst means more reactant molecules have sufficient energy to overcome the energy barrier to reacting (activation energy) so the reaction is faster

13

14

YIELD OF AMMONIA* At each pass through the reactor, only

about 15% of the reactants are converted into products under these conditions, but this is done in a short time period.

* Ammonia is cooled and liquefied at the reaction pressure, & then removed as liquid ammonia.

* The remaining mix of nitrogen and hydrogen gases (85%) are recycled & fed in at the reactant stage.

* The process operates continuously & the overall conversion is about 98%.

15

16

MONITORING OF HABER PROCESS

* incoming gas stream ratio H2:N2 of 3:1 pressure - too low and yield of NH3 drops, too high

shortens the life of the reaction vessel and unsafe – pressure sensors monitor

sensors monitor levels CO and CO2 as poison catalyst

CO(g) + H2O(g) CO2(g) + H2(g)

CO2(g) + H2O(l) + K2CO3(aq) 2KHCO3(aq) CO2 piped to urea plant where reacted with NH3 to form

urea (NH2CONH2) or sold to brewers and soft drink manufacturers

MONITORING OF HABER PROCESS

* optimum temperature in converter temperature sensors monitor as too high damages

catalyst and reduces yield

* activity of catalyst particle size monitored to ensure high surface area

* purity of ammonia produced* energy use

17

18

THE HABER PROCESS

2.3.1 gather and process information from secondary sources to describe the conditions under which Haber developed the industrial synthesis of ammonia and evaluate its significance at that time in world history case study

THE HABER PROCESS* Fritz Haber, German chemist, 1868-

1934* winner of the Nobel Prize in Chemistry

(1918) for the synthesis of ammonia from

its elements* Carl Bosh developed the industrial

stages for the Haber process. The perfection of the Haber-Bosh process encouraged Germany to enter in World War I.

19

Case Study

Demand for fertiliser* sources of fixed nitrogen

Chile saltpetre (NaNO3) exported to Europe in mid-19th century

coal-gas industry – ammoniacal liquor (NH3 in water) by-product processed to (NH4)2SO4

Explosives – nitroglycerineDyestuffs - 1856 start of synthetic

dyes – nitrogenous compounds20

Case Study* all these demands could not be

satisfied by Chile saltpetre

* needed a process to fix atmospheric N2

* 1904-1908 Fritz Haber developed the process of synthesising NH3 from N2 and H2

high pressure, 450oC, catalyst

* Carl Bosch developed it as an industrial process - 30,000 tons by 1913

21

Case StudyPolitical Unrest* Britain and allies controlled the sea-

routes for Chile saltpetre* Germany cut off from this source of

fixed N2

* WWI 1914 plant increased to 120,000 tons and a second plant up and running

* Germany increased munitions increased fertiliser for food production

22

Case Study

Social consequences of Haber process

* prolonged WWI by 1-2 years – almost 1 million more deaths

* vast expansion of production of fixed N2 for fertilisers

23

HTTP://WWW.YOUTUBE.COM/WATCH?V=C4BMMCUXMU8

HABER PROCESSHABER PROCESS

24

3.2.1 deduce the ions present in a sample from

the results of tests

Cations – Ba2+, Ca2+, Pb2+, Cu2+, Fe2+, Fe3+

Anions - PO43-, SO4

2-, CO32-, Cl-

3.3.2 gather, process and present information to describe and explain

evidence for the need to monitor levels of one of the above ions in

substances used in society

* Pb poisoning

* PO43- - eutrophication of

waterways leading to algae “blooms”

26

Chemical Analysis

* Qualitative identify what species are present in a sample

e.g. vitamin tablet contains copper salt

* Quantitative determine the amount/concentration of

species present in a sample

e.g. vitamin tablet contains 1.2mg copper volumetric, gravimetric, instrument - AAS

27

28

Identification of Ions1. A solution contains Cl- ions. Identify

an appropriate cation solution that could be added to detect the presence of these chloride ions.

2. A solution forms a white precipitate with carbonate ions and no precipitate with hydroxide ions. What common cation is most likely present in the solution?

29

Identification of Ions

3. A solution forms a precipitate with a solution of sodium phosphate, no precipitate with sodium sulfate and no precipitate with sodium chromate. What is the identity of the cation?

Identification of Ions

Risk Assessment

* moderately toxic – Ba cpds, AgNO3, (NH4)2MoO4 , CuSO4 , KSCN, NH3 solution

* highly toxic – Pb cpds waste collected in separate beaker – filter PbI2

* corrosive – 4M HNO3, 2M NaOH

30

Identification of Ions

Hazard Minimisation* small quantities* fume cupboard for ammonia

solution, good ventilation* safety glasses (corrosive

solutions), lab coats* work near water supply and wash

hand at end

31

Identification of CationsLead (II)

Pb2+(aq) + 2I-

(aq) PbI2(s)

(canary yellow ppte)Copper(II)Cu2+

(aq) + 2OH-(aq) Cu(OH)2(s)

(light blue ppte)Cu(OH)2(s) + 4NH3(aq) [Cu(NH3)4]2+

(aq)+ 2OH- (complex ion)

(royal blue solution)32

33

Identification of Cations

Iron(II)Fe2+

(aq) + 2OH-(aq) Fe(OH)2(s)

(greenish ppte)

3Fe2+(aq) + 2[Fe(CN)6]3-

(aq) Fe3[Fe(CN)6]2(s)

(dark blue ppte)

Identification of Cations

Iron(III)Fe3+

(aq) + 3OH-(aq) Fe(OH)3(s)

(brown ppte)Fe3+

(aq) + SCN-(aq) FeSCN2+

(aq)

(complex ion)

blood red

34

35

Identification of Cations

CalciumCa2+

(aq) + CO32-

(aq) CaCO3(s)

(white ppte)

BariumBa2+

(aq) + CO32-

(aq) BaCO3(s)

(white ppte)

36

Identification of AnionsCarbonate

CO32-

(aq) + 2H+(aq) CO2(g) + H2O(l)

pH of solution alkalineChloride

Cl-(aq) + Ag+(aq) AgCl(s)

(white precipitate)Sulfate

SO42-

(aq) + Ba2+(aq) BaSO4(s)

(white precipitate)

37

Identification of Anions

Phosphate ammonium molybdate reagent

12(NH4)2MoO4 + PO43- + 3H+

(NH4)3PO4.12MoO3(s) + 12H2O + 21NH3

ammonium phosphomolybdate (yellow precipitate on heating)

3.3.2 gather, process and present information to describe and explain evidence for the need to monitor levels of one of the above ions in substances used in society

39

SPECTROSCOPY

white light

40

SPECTROSCOPY* many substances can be heated to a point

at which they will emit electromagnetic radiation

* excitation of the atoms forces electrons to higher energy levels “excited state”

* movement of the electron to a lower energy level requires the loss of a specific amount of energy corresponding to that transition

* the excited atom can emit this energy as visible, IR or UV radiation

Flame Test - Emission

41

42n=1

n=2

n=3

n=4

Spectrum

UV

IR

Vi s ible

Ground State

Excited State

Excited StateExcited State unstable and drops back down

•Energy released as a photon

•Frequency proportional to energy drop

Excited State

But only as far as n = 2 this time

Flame Emission

* electron normally in Ground State

* energy supplied [ as heat or electricity]

* electron jumps to higher energy level

* now in Excited State - UNSTABLE

* drops back to a lower level

* energy that was absorbed to make the

jump up is now released as a photon

43

44

EMISSION SPECTRUM* each element has unique atoms so emits

an emission spectrum with a unique pattern of colours (wavelengths)

45

EMISSION SPECTRA

H

Hg

Ne

Each element has a unique emission spectrum

46

ABSORPTION SPECTRUM

* when an unexcited substance is exposed to a source of radiation containing the full range of wavelengths is will absorb specific characteristic wavelengths corresponding to the electron transitions to “excited” states

47

ABSORPTION SPECTRUM

* if the light is analysed after it passes through the substance it will show gaps corresponding to the absorbed wavelengths forming an absorption spectrum

* Absorption Spectroscopy is the study of substances by analysing their absorption of specific wavelengths of radiation

H

48

EMISSION AND ABSORPTION

Hydrogen emission spectrum

Hydrogen absorption spectrum

SUBSECTION 3Manufactured products, including

food, drugs and household chemicals, are analysed to determine or ensure their chemical composition

3.2.2describe the use of AAS in

detecting concentrations of metal ions in solutions and

assess its impact on scientific understanding of the effects of

trace elements

USES OF AASTrace Elements* elements needed in small quantities for

proper functioning of plants and animals* e.g. Cu, Zn, Co, Mn* plants absorb minerals from the soil* animals get these minerals from the

plants* if soil is lacking in minerals –

humans/animals may show deficiency diseases

51

USES OF AAS* sensitive analytical methods like AAS

led to the discovery of the role of trace elements in specific biochemical pathways

* soil analysis allows farmers to monitor levels of trace elements – treat problem

* blood and urine analysis can detect trace element deficiencies causing disease – change diet/give supplement

* SSB p. 51, 52

52

USES OF AAS

* AAS far superior to “wet” methods like precipitations tests – slow, do not detect very low concentrations, not as specific (may precipitate more than one ion)

53

3.3.5 gather, process and present information to interpret secondary data from AAS measurements and evaluate the effectiveness of this in pollution control

USES OF AAS

Pollution Control* heavy metals include elements such as

Pb, Hg, Cd, Cr* Hg in water absorbed by some organisms

and concentrated in tissues* oysters/mussels (filter feeders) filter

polluted water and Hg/Cd/Pb concentrates in tissues

* other organisms feed off these and further concentrate heavy metals in their tissues

55

USES OF AAS

* EPA requirements industrial wastewater diluted until [Hg] < 2ppm fish and shellfish contain Hg <= 0.5ppm

* AAS can be used to measure the level of Hg in seafood

* SSB p. 128 Heavy Metals

56

SUBSECTION 5Human activity also impacts on

waterways. Chemical monitoring and management assists in providing safe water for human use and to

protect the habitats of other organisms

5.2.1 Identify that water quality can be determined by considering

* concentration of common ions Cl-, OH-, HCO3

-, NO3-, SO4

2-, CO32-, PO4

3-

Na+, K+, Ca2+, Mg2+

58

* total dissolved solids usually ionic salts

* hardness level of Ca2+ and Mg2+ ions

59

5.2.1 Identify that water quality can be determined by considering

* turbidity clarity of the water reflects level of suspended solids

60

5.2.1 Identify that water quality can be determined by considering

* acidity – measure the pH

* dissolved O2 (DO) high level of dissolved O2 supports a large

variety of aquatic organisms

61

5.2.1 Identify that water quality can be determined by considering

* biochemical O2 demand (BOD) measures how fast the O2 is being used up by

microorganisms may be measured over 5 days BOD5 = DO0 (mg/L) – DO5 (mg/L)

> 5mg/L indicates polluted water

62

5.2.1 Identify that water quality can be determined by considering

Biochemical Oxygen Demand BOD

* Biochemical Oxygen Demand is a measure of how much dissolved oxygen is being consumed as microbes break down organic matter.

* A high demand, therefore, can indicate that levels of dissolved oxygen are falling, with potentially dangerous implications for the river's biodiversity.

* High biochemical oxygen demand can be caused by: high levels of organic pollution, caused usually by poorly

treated wastewater; high nitrate levels, which trigger high plant growth.

* Both result in higher amounts of organic matter in the river. When this matter decays, the microbiological activity uses up the oxygen.

63

64

Town Water Supply

* catchment area sources of contamination

* chemical tests turbidity, dissolved oxygen, pH, nitrate,

phosphate, conductivity/salinity, hardness other - bacteriological

* physical processes sedimentation filtration – anthracite, sand, gravel

65

Town Water Supply

66

Town Water Supply

* chemical processes/additives alum/polyelectrolyte to flocculate clay particles chlorine – disinfection fluoride – dental protection lime (CaO) – raise pH to neutral as alum

acidifies water

Filtration

67

Membrane Filters

68

AAS & Water Monitoring

ADVANTAGES* little sample preparation needed* each metal ion in a mixture of ions can be

determined * high sensitivity – detects ppm or ppb- ideal

for use in water quality analysis* cost effective compared to more labour

intensive techniques like titrations, precipitations

* fast, automated technique so can measure large number of samples quickly

69

AAS & Water Monitoring

* disadvantage – does not measure biological measures of water quality dissolved oxygen BOD bacterial contamination

POTABLE water is water of sufficiently high quality that it can be consumed or used with low risk of immediate or long term harm.

70

5.3.2 Eutrophication of Water

* the enrichment of a water body with nutrients such as nitrate and phosphate

* increases the possibility of algal blooms* main sources of phosphate

sewage – decomposition of organic matter, detergents fertiliser runoff

* effects – text p. 286, SSB p. 125-127* monitoring – text p. 288, SSB p. 139

71

5.3.2 Eutrophication of Water

* Phosphates used as builders in detergents – complex with calcium and magnesium ions (hard water)

* Calcium and magnesium ions can cause small colloidal particles like clay to flocculate which soils clothes in the wash.

* Builders give detergents better cleaning power.

* Sodium zeolite is now being used to replace phosphates in detergents

* Zeolites are complex compounds containing metal ions bound to an aluminosilicate lattice – calcium and magnesium ions are exchanged for sodium ions so softens the water

* Zeolites cannot cause the eutrophication problems associated with phosphates

72

5.3.2 Eutrophication of Water

* Algal bloom likely [phosphate] > 0.05 ppm dam/lake [phosphate] > 0.1 ppm river/stream (higher

value as likely to be flowing)

73

5.3.2 Eutrophication of Water

74

75

2010 Water Quality - Wonga

Parameter Excellent House Lagoon

Bagnell’s Lagoon

Tank

pH 6.0-7.5 6.5 6.5 5.2

TurbidityNTU

< 15 13 26 <10

SalinityS/cm

< 100 465 112 20

TemperatureoC

11.4 11.6 11.4

Oxygen Sat.%

80-90 37 55 91

Hardness (ppm)

< 75 19 40 0

NO3- (mg/L) < 0.05 below

detectable level

below detectable

level

0.88

PO43- (mg/L) < 0.01 below

detectable level

6 20

76

2011 Water Quality - Wonga

Parameter Rating Black

Lagoon

Bagnell’s Lagoon

Tank

Temperature

(oC)

Poor

0-5

Good

5-20

Poor

20-30

8.8 13 9

pH Poor

<6

Healthy

6-8

Poor

>8

5 6 5

Conductivity

(uS/cm)

Healthy

<300

Fair

300-800

Poor

>800

110 520 10

Turbidity

(NTU)

Healthy

<10

Fair

15-30

Poor

>30

29 17.5 <10

Phosphates

(ppm)

Good

0-5

Fair

5-15

Poor

15-30

5 5 4

Nitrites

(ppm)

Good

<0.1

Fair

<0.2

Poor

<0.4

0.2 0.1 <0.15

Hardness

(ppm)

Soft

0-50

Hard

120

Very hard

250-425

50 120 0

Oxygen Saturation

(%)

Poor

<80

Good 80-90Healthy waterways need O2 level > 6mg/L

High quality fresh water 9mg/L

40 25 51

Destructive/Non-destructive Testing

Determination of Dissolved Solids

* Using a conductivity meter measures the conductivity

(concentration of ions) in the sample does not change the sample so it can

be used for further testing e.g. pH

77

Destructive/Non-destructive Testing

* Filtration and evaporation procedure destroys sample some salt left in filter paper spitting of salt when heating potentially lower result soot on evaporating basin if not always blue

flame may potentially give a higher result

78