Download Reaction types and Stoichiometry

Chemical Reactions

All chemical reactions show a conservation of mass, energy and charge.

A balanced chemical equation represents conservation of atoms.

The coefficients in a balanced chemical equation can be used to determine mole ratios
in the reaction, and can further be used to predict relationships about amounts
between products and reactants.

The molar mass of a substance is the sum of the atomic masses of its atoms. The
molar mass (gram formula mass) equals the mass of one mole of that substance.
Ex Fe2O3 molar mass is equal to 2 x 55.85 grams + 3 x 16 grams =159.7 grams

The percent composition by mass of each element in a compound can be calculated
mathematically.
Ex C6H12O6 molar mass is equal to 180 grams
The percent composition of each of it’s components are
6(12.01)
180

x 100 = 40 %C
12(1.01)
180
x 100 = 7% H
6(16)
180
x 100 = 53 % O
Types of chemical reactions include synthesis, decomposition, single replacement, and
double replacement.
Synthesis
A + B → AB
ex. 2Na + Cl2 → 2NaCl
Decomposition AB → A + B 2 NaCl → 2Na +Cl2
Single Replacement A + BD→ AD + B
or
E + BD → BE + D
Mg +2 HCl → MgCl2 +H2 or F2 + NaCl → NaF + Cl2

*A&B are metals and E& D are nonmetals
Combustion CxHy +O2 → CO2 +H2O
Practice Questions
1. Which is an example of a synthesis reaction?
A
B
C
D
2.
HCl + KOH→KCl + H2O
Pb(NO3)2 + 2HBr→ PbBr2 + 2HNO3
C + O2 → CO2
Mg + H2SO4 → MgSO4 + H2
Which of the following equations is balanced
3. If 3.50 g of H2S are used in the above reaction, what will be the theoretical yield of
water in grams?
A
B
C
D
0.102 g
0.185 g
1.85 g
185 g
4. Carbon disulfide is prepared industrially by reacting carbon with sulfur
dioxide according to the above equation. If 5.9 moles of carbon react, how many
moles of CS2 are produced?
A
B
C
D
0.077 moles
1.2 moles
1.5 moles
30 moles
5. How many milliliters of 2.00 M H2SO4 are needed to provide 0.250 mole of H2SO4?
A
B
C
D
125 mL
1.25 x 101 mL
8.00 x 103 mL
8.00 M
6. When copper reacts with silver nitrate according to the equation, the number of
grams of copper required to produce 432 grams of silver is —
A
B
C
D
31.5 g
127 g
216 g
252 g
7. The number of grams of oxygen required for the complete combustion of 4.00
grams of methane (CH4) is —
A
B
C
D
4.00 g
8.00 g
16.0 g
32.0 g
Zn + 2HCl → ZnCl2 + H2
8. If 0.600 gram of zinc is used, what is the amount of zinc chloride that is produced
in the above reaction?
A
B
C
D
0.125 gram
1.25 grams _
12.5 grams
0.018 gram

2H2(g) + 02(g)  2H2O(g)
9. How many liters of oxygen are required to produce 2 liters of water at STP?
A
B
C
D
1
2
3
4
10.
When magnesium metal (Mg) is burned, it forms MgO. How many moles of
oxygen gas (O2) are needed to burn 10 moles of Mg?
A
B
C
D
2
5
10
20
2KOH + H2SO4 → 2H2O + K2SO4
11.
What mass of potassium hydroxide is required to react completely with 2.70
g of sulfuric acid to produce potassium sulfate and water?
A
B
C
D
4.73 g
3.09 g _
2.36 g
1.54 g
W+X→Y+Z
12.
How many grams of product Z will be formed if 12.0 g of W react with 10.0 g
of X to form 8.0 g of product Y in the reaction shown?
A
B
C
D
8.0 g
10.0 g
12.0 g
14.0 g _
N2 + 3H2 → 2NH3
13.
If 6 liters of hydrogen gas are used, how many liters of nitrogen gas will be
needed for the above reaction at STP?
A 2 liters
B
3 liters
C
4 liters
D
12 liters
14.
In the combustion of ethane, how many moles of CO2 can be produced from
1.00 mole of C2H6?
A
B
C
D
0.500 mole
1.00 mole
2.00 moles
4.00 moles
15. Which reaction type best describes the reaction above?
A
B
C
D
Combination
Decomposition
Single replacement
Combustion
16. What type of reaction does this illustration represent?
A
B
C
D
Decomposition
Synthesis
Single-replacement
Double-replacement
17. The type of reaction represented by the above equation is —
A
B
C
D
single-replacement
double-replacement
synthesis
decomposition
18. A balanced chemical equation has equal numbers of atoms of each type on both sides of
the equation. This illustrates the principle of —
A
B
C
D
conservation of energy
conservation of mass
action and reaction
natural selection
Aluminum +Sulfuric Acid  Aluminum Sulfate + Hydrogen Gas
19. Which of the following is the balanced chemical equation for the reaction shown above?
A
Al + H2SO4  Al2(SO4)3 + H2
B
2Al + 3H2SO4  Al2(SO4)3 + 3H2 _
C
2Al + 3H2SO4  Al2(SO4)3 + H2
D
2Al + H2SO4  Al2(SO4)3 + H2
20. Which of these is the general formula for a double-replacement reaction?
A
B
C
D
A +B  AB
AB + XY  BA + YX
AB + XY  AY + XB
A + B + XY  AX + BY
21. The appropriate model for a decomposition reaction is —
Al + HCl  AlCl3 + H2
22. When the above equation is balanced, the coefficient of the hydrochloric acid will be —
A
B
C
D
2
3
4
6_
23. Which set of coefficients will balance this equation?
A
B
C
D
1, 3, 1, 1
2, 3, 2, 6
2, 6, 2, 3
3, 6, 3,
24. Which half-reaction represents reduction?
A
B
C
D
Cu0 → Cu+2 + 2eFe+2 → Fe+3 + 1eAg+1 + 1e- → Ag0
Al0 → Al+3 + 3e-
25. Which of the following best represents the reaction between hydrochloric acid and sodium
hydroxide?
A
B
C
D
2HCl + 2NaOH → Na(OH)2 + H2Cl2
HCl2 + 2Na(OH)2 → 2H2O +2NaCl + OH
HCl + NaOH → H2O + NaCl
2HCl + Na(OH)2 → 2H2 + NaCl + O2





CH4 (g) + 2O2 ______ (g)+ 2H2O(g)
26. Which completes the chemical equation above?
A
B
C
D
CO2
CO3
CO
C
27. Which of the following models a synthesis reaction?
A
B
C
D
Answers
1C
16A
2C
17A
3C
18B
4B
19B
5A
20C
6B
21A
7C
22D
8B
23C
9A
24C
10B
25C
11B
26A
12D
27C
13A
14 C
15C