Chapter 3 Stoichiometry: Calculations with Chemical Formulas and Equations

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Chapter 3 Stoichiometry: Calculations with Chemical Formulas and Equations

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0.5 mol of carbon is combusted with 1.0 mol of oxygen gas. ... g of carbon are combusted with. 32.0 g of ... 3.0 moles Mg are combusted with 2.0 moles O2. ... –

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Title: Chapter 3 Stoichiometry: Calculations with Chemical Formulas and Equations

1
Chapter 3Stoichiometry Calculations with
Chemical Formulasand Equations
2
The following equation is unbalanced CS2 O2
CO2 SO2 What is the correct
balanced equation?
3
Correct Answer

CS2 2 O2 CO2 2 SO2
2 CS2 12 O2 2 CO2 4 SO2
CS2 3 O2 CO2 2 SO2
CS2 6 O2 CO2 2 SO2

This is the only case where the number of each
type of atom is the same on both the reactant and
product sides of the equation.
4
Which of the following is the correct, balanced
chemical equation for the combustion of ethanol
(C2H5OH)?

C2H5OH O2 CO2 H2O
C2H5OH 3 O2 2 CO2 3 H2O
C2H5OH 6 O2 4 CO2 6 H2O
2 C2H5OH 7 O2 4 CO2 6 H2O

O
O
5
Correct Answer

C2H5OH O2 CO2 H2O
C2H5OH 3 O2 2 CO2 3 H2O
C2H5OH 6 O2 4 CO2 6 H2O
2 C2H5OH 7 O2 4 CO2 6 H2O

O
O
O
6
If the empirical formula of a compound is C2H2N
but the molecular weight is 160 g/mol, what is
the molecular formula?

C2H2N
C4H4N2
C6H8N3
C8H8N4
None of the above choices is correct.

7
Correct Answer

C2H2N
C4H4N2
C6H8N3
C8H8N4
None of the above choices is correct.

FW C2H2N (24 2 14) g/mol 40 g/mol MW/FW
160/40 4 Thus, molecular formula is 4?
empirical formula 4(C2H2N) C8H8N4
8
How many fluorine atoms are present in 2.0 moles
of AlF3?

3.0 ? 1023
6.0 ? 1023
1.2 ? 1024
3.6 ? 1024
None of the above answers is correct.

9
Correct Answer

3.0 ? 1023
6.0 ? 1023
1.2 ? 1024
3.6 ? 1024
None of the above answers is correct.

(2.0 moles AlF3)(6.0 ? 1023 molecules AlF3/mole
AlF3) (3 atoms F/1 molecule AlF3) 3.6 ? 1024
10
Which of the following samples has the largest
number of atoms?

28 g Si
28 g CO
28 g N2
15 g C2H4
All of the above have equal numbers of atoms.

11
Correct Answer

28 g Si
28 g CO
28 g N2
15 g C2H4
All of the above have equal numbers of atoms.

28 g Si has 1 mole of atoms, whereas 28 g of CO
and N2 have 2 moles of atoms, even though they
also have only 1 mole substance. However, there
are 6 atoms for every 1 mole of C2H4, so in this
case there are slightly more than 3 moles worth
of atoms.
12
The molecular mass for the compound, XClO3, is
122.5 amu. The atomic mass of X is equal to ____
amu, which is the element ____.

1.0 H
6.9 Li
23.0 Na
39.1 K
85.5 Rb

13
Correct Answer

1.0 H
6.9 Li
23.0 Na
39.1 K
85.5 Rb

MW 122.5 amu AW X AW Cl 3(AW O) 122.5 amu
? AW Cl ? 3 (AW O) AW X 122.5 amu ? (35.45 amu)
? 3 (16.0 amu) AW X 122.5 ? 35.45 amu ? 48.0
amu AW X AW X 39.1 amu
14
When the chemical equation, C4H10(g) O2(g)
H2O(g) CO2(g), is balanced, the
stoichiometric coefficients are, respectively

1, 4, 5, 4
2, 13, 10, 8
2, 9, 8, 10
2, 7, 4, 5

15
Correct Answer

1, 4, 5, 4
2, 13, 10, 8
2, 9, 8, 10
2, 7, 4, 5

16
The combustion of methane (CH4) is shown below
CH4(g) 2 O2(g) 2 H2O(l) CO2(g)
How many grams of water are produced in the
combustion of 1.0 moles of methane?

16 g
32 g
36 g
48 g

17
Correct Answer

16 g
32 g
36 g
48 g

(1.0 mole CH4)(2 moles H2O/1 mole CH4)
(18 g H2O/1 mole H2O) 36 g
18
0.5 mol of carbon is combusted with 1.0 mol of
oxygen gas. Which of the following statements is
correct?

There is a molar excess of carbon, not all carbon
is consumed.
There is a molar excess of oxygen, not all oxygen
is consumed.
There are stoichiometrically equivalent amounts
of carbon and oxygen gas.

19
Correct Answer

There is a molar excess of carbon, not all carbon
is consumed.
There is a molar excess of oxygen, not all oxygen
is consumed.
There are stoichiometrically equivalent amounts
of carbon and oxygen gas.

C and O2 react in a 11 stoichiometric ratio,
therefore there must be excess O2 because there
was a larger initial number of moles of it.
20
0.5 mol of carbon is combusted with 1.0 mol g of
oxygen gas. How many moles of carbon dioxide are
produced?

1.5 mol
1.0 mol
0.5 mol
2.0 mol

21
Correct Answer

1.5 mol
1.0 mol
0.5 mol
2.0 mol

C and O2 react in a 11 stoichiometric ratio,
therefore C must be the limiting reagent and O2
must be the excess reagent. Initially, (0.5
moles C)(1 mole CO2/1 mole C) 0.5 mole CO2
22
24.0 g of carbon are combusted with 32.0 g of
oxygen gas. How many grams of carbon dioxide are
produced?

56.0 g
88.0 g
28.0 g
44.0 g

23
Correct Answer

56.0 g
88.0 g
28.0 g
44.0 g

C and O2 react in a 11 stoichiometric ratio.
Initially, (24.0 g C) ? (1 mole C/12.0 g C) ? (1
mole CO2/1 mole C) 2.0 mole CO2 (32.0 g O2) ?
(1 mole O2/32.0 g O2) ? (1 mole CO2/1 mole O2)
1.0 mole CO2 Thus, O2 is limiting, and 1.0 mole
of CO2 is 44.0 g.
24
3.0 moles Mg are combusted with 2.0 moles O2.
What is the limiting reagent and how many moles
of the excess reagent remain?

Magnesium, 0.5 mole
Magnesium, 1.0 mole
Oxygen gas, 0.5 mole
Oxygen gas, 1.0 mole

25
Correct Answer

Magnesium, 0.5 mole
Magnesium, 1.0 mole
Oxygen gas, 0.5 mole
Oxygen gas, 1.0 mole

Mg and O2 react in a 21 stoichiometric ratio.
Initially, (3 mole Mg)(2 mole MgO/2 mole Mg)
3.0 mole MgO (2 mole O2)(2 mole MgO/1 mole O2)
4 mole MgO Thus, Mg is limiting, and 3 mol Mg
will consume 1.5 mol of O2, leaving 0.5 mole of
O2.
26
How many oxygen atoms are presentin MgSO4 7
H2O?