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WebStudies test and Tutorial

Tut Test 5 (formative assessment):Friday, 12th 12:00 → Tuesday, 16th 18:00

Tutorial 6: Thursday 18th 14:00

the molethe moledefining the molemolar massamount-mass-number conversionsmass percentage

determine formula of unknown compounddetermine formula of unknown compoundempirical/molecular formulas

writing & balancing chemical equationswriting & balancing chemical equationscalculating quantities (stoichiometry)calculating quantities (stoichiometry)

mole-mole conversions from equationslimiting reactantsreaction yields

fundamentals: solution stoichiometryfundamentals: solution stoichiometrymolarityamount-mass-number conversionsdiluting molar solutionsreactions in solution

reading assignment: chapter 2reading assignment: chapter 2videos WebStudiesvideos WebStudies

learning opportunities

peer-assisted group learning (PAGL)peer-assisted group learning (PAGL)interactive –style teachinginteractive –style teaching

enquiry based learningenquiry based learning

prepare for contact session:prepare for contact session:you do assigned readingyou watch video clips Blackboardyou work related sample problems text book/webyou reflect: wonder, think about the concepts

during contact session:during contact session:we ask & test understanding of conceptswe put up questions and discuss the contentyour group discusses/decides a responseyour scribe (guy in the middle) communicatesyour group compares group behind/frontno-one calls answers, chews, misbehaves, etc.

the molethe moledefining the molemolar massamount-mass-number conversionsmass percent

determine formula of unknown compounddetermine formula of unknown compoundempirical/molecular formulas

writing & balancing chemical equationswriting & balancing chemical equationscalculating quantities (stoichiometry)calculating quantities (stoichiometry)

mole-mole conversions from equationslimiting reactantsreaction yields

fundamentals: solution stoichiometryfundamentals: solution stoichiometrymolarityamount-mass-number conversionsdiluting molar solutionsreactions in solution

this lecture

You make sandwiches that contain exactly 2 slices of bread and 1 slice of ham. If you have 23 slices of ham and 50 slices of bread, how many sandwiches can you make?

limiting reactants

a)a)

b)b)

c)c)

d)d)

50

25

23

none of the above

2 slices bread + 1 ham → 1 sandwich

50 slices 23 slices

theory

2 bread1 ham

given

50 bread23 ham

given

2.17 bread1 ham

(theory)(given amounts)

limiting reactants

a)a)

b)b)

c)c)

d)d)

You want to make sandwiches that specifically contain 2 slices of bread, 1 slice of ham and 3 slices of pickles. How many sandwiches can you make if you have 31 slices of bread, 17 slices of ham and 42 slices of pickles?

14

15

17

none of the above

2 bread + 1 ham + 3 pickles → 1 sandwich31 17 42

31 bread × 1 sandwich2 bread

17 ham × 1 sandwich

1 ham

42 pickles × 1 sandwich3 pickles

= 15.5 sandwich

= 17

= 14

limitinglimitingtheory

given amounts

a)a)

b)b)

c)c)

d)d)

limiting reactants

Consider the reaction stated below. If you reacted 4 moles of N2 and 6 moles of H2, which is the limiting reactant?

a) N2

b) H2

c) NH3

d) none of the above

NN22(g) + 3 H(g) + 3 H22(g) (g) → 2 NH 2 NH33(g)(g)

stoichiometry:3 mol H2

1 mol N2

given:6 mol H2

4 mol N2=

1.5 mol H2

1 mol N2

(theory)b)

(theory)

(given)

limitinglimiting

A reaction vessel contains 6 moles of N2 and 4 moles of H2 that reacts according to the reaction stated below. Which is the limiting reactant?

NN22 + 3 H + 3 H22 → 2 NH 2 NH33

limiting reactants

a)a)

b)b)

c)c)

N2

H2

NH3

NH3 (mol): 26 mol N 3

2

2 mol NH1 mol N

= 12 mol NH3

NH3 (mol): 24 mol H 3

2

2 mol NH3 mol H

= 2.7 mol NH33 H2

1 N2theory

4 H2

6 N2given

0.6 H2

1 N2given

limiting

OROR

limiting

a)

b)

c)

d)

e)

limiting reactants

Consider the reaction stated below. If you had 4 moles of N2 and 6 moles of H2, what is the maximum amount of NH3 one could produce in this reaction?

a) 8 moles NH3 b) 4 moles NH3

c) 12 moles NH3

d) 6 moles NH3

N2(g) + 3 H2(g) → 2 NH3(g)

NH3 (mol): 26 mol H 3

2

2 mol NH3 mol H

NH3 (mol): 24mol N 3

2

2 mol NH1 mol N

b)

= 4 mol NH3

= 8 mol NH3

Asirvatham, 2010

Examine the molecular view of the reaction between AB and B2 in the gas phase:

The correct statement about this reaction is:

a) The balanced equation: AB + B2 → AB3

b) AB and B2 are initially in stoichiometric amountsc) AB is the limiting reactantd) The product of the reaction is A2B

a)a)

b)b)

c)c)

d)d)

e)e)balanced equation: 2 AB + B2 → 2 AB2

c)

limiting reactants

excess limitingCH4 + 2 O2 → CO2 + 2 H2O

given: 2 mole O2

5 mol CH4

=

wantwantstoichiometry:

2 mole O2

1 mol CH4

havehave

= 21

0.41

Wood, 2006

Identify whether this presentation represents the combustion of methane (CH4) with

a) stoichiometric amount of oxygen b) methane limitingc) oxygen limiting

c)c)

a)a)

b)b)

c)c)c)c)

b)b)

c)c)c)c)

wantwant

havehave

limiting excessCH4 + 2 O2 → CO2 + 2 H2O

given: 7 mole O2

2 mol CH4

stoichiometry:2 mole O2

1 mol CH4

= 21

=3.51

Wood, 2006

Identify whether this presentation represents the combustion of methane (CH4) with

a) stoichiometric amount of oxygen b) methane limitingc) oxygen limiting

c)c)

a)a)

b)b)

c)c)c)c)

b)b)

b)b)

wantwant

havehave

CH4 + 2 O2 → CO2 + 2 H2O

given: 6 mole O2

3 mol CH4

=

stoichiometry:2 mole O2

1 mol CH4

= 21

Wood, 2006

Identify whether this presentation represents the combustion of methane (CH4) with

a) stoichiometric amount of oxygen b) methane limitingc) oxygen limiting

21

c)c)

a)a)

b)b)

c)c)c)c)

b)b)

a)a)

2 SO2 SO22(g) + O(g) + O22(g) (g) → 2 SO 2 SO33(g)(g)

Given 3.0 moles of SO2. O2 would be the limiting reactant if we had less than ___ mol O2

limiting reactants

Given 5 moles of O2. SO2 would be the limiting reactant if we had less than ___ mol SO2

Given 3.5 moles of O2. SO2 is in excess if we had more than ___ mol SO2

Given 1.5 moles of SO2. O2 is in excess if we had more than ____ mol O2

1.51.5

1010

7.07.0

0.750.750.75

1.5

10

7.0

a)a)

b)b)

c)c)

d)d)

e)e)3.5

If you have 8 moles of hydrogen gas and all the oxygen gas you need, how many moles of water can you make?

a)a)

b)b)

c)c)

d)d)

e)e)

a) 1 molb) 2 molc) 4 mold) 8 mole) 16 mol

water (mol): 28 mol H 2

2

2 mol H O2 mol H

calculations with equations

O2 + 2 H2 → 2 H2O

If you have all the hydrogen gas that you need and 8 moles of oxygen gas, how many moles of water can you make?

28 mol O 2

2

2 mol H O1mol O

If you have 8 moles of hydrogen gas and 9 moles of oxygen gas, how many moles of water can you make?

stoich: 2 mol H2

1 mol O2

= 21

given: 8 mol H2

9 mol O2

= 0.89

1

28 mol H 2

2

2 mol H O2 mol H

limiting

limiting reactants

tip:whenever the mass or amount of both reactants are given, you can bet your bottom dollar that one of the reactants will be limiting

challenging problem:sodium hydroxide reacts with carbon dioxide to give solid sodium carbonate and liquid water. when 1.70 mol sodium hydroxide is reacted with 1.00 mol carbon dioxide, the actual yield was found to be 93.3%. how many grams of sodium carbonate was produced?