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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

reading assignment: chapter 2

videos WebStudies

the mole

defining the mole

molar mass

amount-mass-number conversions

mass percentage

determine formula of unknown compound

empirical/molecular formulas

writing & balancing chemical equations

calculating quantities (stoichiometry)

mole-mole conversions from equations

limiting reactants

reaction yields

fundamentals: solution stoichiometry

molarity

amount-mass-number conversions

diluting molar solutions

reactions in solution

peer-assisted group learning (PAGL)

interactive –style teachingenquiry based learning

learning opportunities

prepare for contact session:

you do assigned readingyou watch video clips Blackboard

you work related sample problems text book/web

you reflect: wonder, think about the concepts

during contact session:

we ask & test understanding of concepts

we put up questions and discuss the content

your group discusses/decides a response

your scribe (guy in the middle) communicates

your group compares group behind/front

no-one calls answers, chews, misbehaves, etc.

this lecture

the mole

defining the mole

molar mass

amount-mass-number conversions

mass percent

determine formula of unknown compound

empirical/molecular formulas

writing & balancing chemical equations

calculating quantities (stoichiometry)

mole-mole conversions from equations

limiting reactants

reaction yields

fundamentals: solution stoichiometry

molarity

amount-mass-number conversions

diluting molar solutions

reactions in solution

limiting reactants

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?

2 slices bread + 1 ham → 1 sandwich

(theory)

50 slices

23 slices

(given amounts)

2.17 bread

1 ham

50 bread

23 ham

2 bread

1 ham

given

theory

a)

compare

50

25

b)

bread:ham ratio

given

c)

23

bread more than needed

none of the above

d)

limiting reactants

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?

theory

limiting

2 bread + 1 ham + 3 pickles → 1 sandwich

given amounts

31

17

42

= 15.5 sandwich

31 bread ×

a)

14

1 sandwich1 ham

1 sandwich3 pickles

1 sandwich2 bread

= 17

17 ham ×

15

b)

= 14

42 pickles ×

c)

17

none of the above

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

N2(g) + 3 H2(g) → 2 NH3(g)

(theory)

b)

stoichiometry:

1.5 mol H2

1 mol N2

3 mol H2

1 mol N2

(theory)

a)

limiting

6 mol H2

4 mol N2

b)

given:

=

c)

(given)

d)

limiting reactants

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?

limiting

N2 + 3 H2→ 2 NH3

NH3 (mol):

= 12 mol NH3

limiting

NH3 (mol):

= 2.7 mol NH3

OR

a)

N2

0.6 H2

1 N2

4 H2

6 N2

3 H2

1 N2

H2

b)

given

theory

given

c)

NH3

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)

b)

a)

NH3 (mol):

= 4 mol NH3

b)

NH3 (mol):

= 8 mol NH3

c)

d)

e)

limiting reactants

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

The correct statement about this reaction is:

a)

a) The balanced equation: AB + B2 → AB3

b) AB and B2 are initially in stoichiometric amounts

c)AB is the limiting reactant

d)The product of the reaction is A2B

b)

c)

c)

d)

balanced equation:

2 AB + B2→2 AB2

e)

Asirvatham, 2010

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

a) stoichiometric amount of oxygen

b)methane limiting

c) oxygen limiting

c)

c)

excess

limiting

CH4 + 2 O2 → CO2 + 2 H2O

2 mole O2

5 mol CH4

2 mole O2

1 mol CH4

2

1

want

stoichiometry:

=

a)

0.4

1

have

b)

b)

given:

=

c)

c)

c)

Wood, 2006

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

a) stoichiometric amount of oxygen

b)methane limiting

c) oxygen limiting

b)

limiting

excess

CH4 + 2 O2 → CO2 + 2 H2O

2 mole O2

1 mol CH4

7 mole O2

2 mol CH4

2

1

stoichiometry:

=

want

a)

3.5

1

have

given:

=

b)

b)

c)

c)

c)

Wood, 2006

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

a) stoichiometric amount of oxygen

b)methane limiting

c) oxygen limiting

a)

CH4 + 2 O2 → CO2 + 2 H2O

2 mole O2

1 mol CH4

6 mole O2

3 mol CH4

2

1

stoichiometry:

=

want

a)

have

21

given:

=

b)

b)

c)

c)

c)

Wood, 2006

limiting reactants

2 SO2(g) + O2(g) → 2 SO3(g)

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

1.5

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

10

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

7.0

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

a)

0.75

0.75

b)

1.5

c)

10

d)

7.0

3.5

e)

calculations with equations

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

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

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

O2+ 2 H2→2 H2O

a)1 mol

b)2 mol

c)4 mol

d)8 mol

e)16 mol

stoich:

21

=

2 mol H2

1 mol O2

8 mol H2

9 mol O2

limiting

a)

0.891

given:

=

b)

c)

d)

e)

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?