Harvard University Stoichemistry Practice Problems

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I would like these equations balanced and the second part to the problems answered please.

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8.3c Stoichiometry Practice Problems Directions: Balance the following equations and use stoichiometry to solve. Show all unit cancellation and work! 1. If 95 grams of iron are reacted with sulfur to produce iron (III) sulfide, how many grams of sulfur is used in the reaction? a. Balance the Equation: Fe + S → Fe2S3 b. how many grams of sulfur is used in the reaction? 2. If 84.9 grams of iron are reacted with oxygen gas to produce iron (III) oxide, what mass of oxygen is used in the reaction? a. Balance the Equation: Fe + O2 → Fe2O3 b. What is the mass of oxygen is used in the reaction? 3. Nitrogen gas and hydrogen gas react to make ammonia in the Haber process. How many liters of nitrogen are needed at STP to react with 85.00 grams of hydrogen? a. Balance the Equation: N2 + H2 → NH3 b. How many liters of nitrogen are needed at STP to react with 85.00 grams of hydrogen? 4. A student placed 16.5 g of aluminum metal into hydrochloric acid. All of the aluminum reacted to form aluminum chloride and hydrogen gas. a. Balance the Equation: Al b. + HCl → AlCl3 + H2 How many grams of hydrogen gas and aluminum chloride were produced? 5. If 32 grams of Aluminum are reacted with sulfur to produce Aluminum sulfide, how many grams of sulfur are used in the reaction? a. Balance the Equation: Al + S → Al2S3 b. How many grams of sulfur are used in the reaction? 6. If 59.3 grams of Sodium is reacted with oxygen gas to produce Sodium oxide, what mass of Sodium oxide is produced in the reaction? a. Balance the Equation: Na b. + O2 → What mass of sodium oxide is produced in the reaction? Na2O 7. Magnesium hydroxide and hydrochloric acid react to make magnesium chloride and water. How many liters of magnesium hydroxide are needed at STP to react with 2.9 L of hydrochloric acid? a. Balance the Equation: Mg(OH)2 + HCl → MgCl2 + H2O b. How many liters of magnesium hydroxide are needed at STP to react with 2.9 L of hydrochloric acid? 8. A student placed 3.56 g of aluminum metal into iron (III) oxide. All of the aluminum reacted to form aluminum oxide and iron. How many grams of aluminum oxide and iron were produced? a. Balance the Equation: Al + Fe2O3 → Al2O3 + Fe b. How many grams of aluminum oxide and iron were produced?
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8.3c Stoichiometry Practice Problems
Directions: Balance the following equations and use stoichiometry to solve. Show all unit cancellation and
work!
1. If 95 grams of iron are reacted with sulfur to produce iron (III) sulfide, how many grams of sulfur is
used in the reaction?
a. Balance the Equation:
2 Fe
+
3S

Fe2S3

b. how many grams of sulfur is used in the reaction?
Atomic mass iron = 55.845 g / mol
Atomic mass of sulfur = 32.06 g / mol
First use the atomic mass of iron to convert to moles of iron. Then use the molar ratio to convert
from moles of iron to moles of sulfur. Final use the atomic mass of sulfur to find the mass of
sulfur.
95 g Fe x (1 mol Fe) / (55.845 g Fe) x (3 mol S) / (2 mol Fe) x (32.06 g S) / (1 mol S) = 82 g S

2. If 84.9 grams of iron are reacted with oxygen gas to produce iron (III) oxide, what mass of oxygen is
used in the reaction?
a. Balance the Equation:
4 Fe

b.

+

3O2



2Fe2O3

What is the mass of oxygen is used in the reaction?

Atomic mass of Fe = 55.845 g / mol
Molar mass of O2 = 2(15.999) = 31.998 g / mol
84.9 g Fex (1 mol Fe) / (55.845 g Fe) x (3 mol O2) / (4 mol Fe) x (31.998 g O2) / (1 mol O2) = 36.5 g
O2

3. Nitrogen gas and hydrogen gas react to make ammonia in the Haber process. How many liters of
nitrogen are needed at STP to react with 85.00 grams of hydrogen?

a. Balance the Equation:

N2 +

3H2



2NH3

b. How many liters of nitrogen are needed at STP to react with 85.00 grams of hydrogen?
Molar mass N2 = 2(14.007) = 28.014 g / mol
Molar mass H2 = 2(1.008) = 2.016 g / mol
Molar volume at STP = 22.4 L / mol
85.00 g H2 x (1 mol H2) / (2.016 g H2) x (1 mol N2) / (3 mol H2) x (22.4 L N2) / (1 ...


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