Stochiometry

Sample Test

Name: ___________________

For each question below, show all units, calculations and significant digits. If the balanced equation is not given, you will have to write it.

1. Balance the equation below and then answer the questions following. Use significant digits.

____ P + ____ F₂ ____ PF₃

a. How many moles of F2 are required to react with 5.00 moles of P? (3)

b. How many moles of PF3 are produced when 6.00 moles of F2 react? (3)

2. Iron (55.85 g/mol) is an important metal that can be produced by heating aluminum metal (26.98 g/mol) and iron (III) oxide (159.70 g/mol).

a. Write the balanced equation for this reaction. (2)

b. Determine the number of moles of iron (III) oxide required to produce 0.75 moles of iron metal. (3)

c. How many grams of aluminum metal are required for every 500 grams of iron metal produced? (4)

3. The formation of aluminum oxide from its elements is represented by this equation:

2 Al + 3 O₂ 4 Al₂O₃

a. How many moles of aluminum oxide are produced by 2.50 moles of oxygen gas? (3)

b. How many grams of aluminum oxide (101.96 g/mol) are produced when 100 grams of aluminum metal (26.98 g/mol) react? (4)

c. If 0.500 moles of oxygen gas react, how many grams of aluminum oxide (101.96 g/mol) are produced? (4)

4. A white precipitate can be produced by the reaction of potassium hydroxide with magnesium nitrate.

potassium hydroxide + magnesium nitrate potassium nitrate + magnesium hydroxide

Determine the number of moles of potassium hydroxide required to produce 2.50 mol of precipitate. (5)

5. Ammonia (NH₃) (17.04 g/mol) will react with nitrogen monoxide (NO) (30.01 g/mol) to produce nitrogen gas (28.02 g/mol) and water (18.02 g/mol). Predict the mass of nitrogen formed when 1000 grams of ammonia react. (5)

6. Magnesium (24.31 g/mol) reacts with hydrochloric acid (36.46 g/mol) to produce hydrogen gas (2.02 g/mol) and magnesium chloride (95.21g/mol). Calculate the number of grams of magnesium needed to produce 2.50 moles of hydrogen gas. (5)

7. A piece of copper (63.55 g/mol) is dropped into a solution of silver nitrate to produce silver metal (107.87 g/mol) and a solution of copper (II) nitrate. The silver metal is recovered by filtration and dried overnight.

The following data was recorded:

a. Write the balanced equation for this reaction above. (2)

b. Using the data above, calculate the theoretical yield of silver metal. (4)

c. Calculate the per cent yield (nearest whole number). (2)

d. Calculate the number of copper atoms involved in this reaction. (2)

e. Calculate the number of moles of silver nitrate needed to react with all of copper metal? (3)

8. Iron metal reacts with bromine to produce iron (III) bromide. Suppose that you have 10.0 mol of iron and 10.0 mol of bromine.

2 Fe (10.0 mol) + 3 Br₂ (10.0 mol) -----> 2 FeBr₃

a. Identify the limiting reagent. Please show your work. (4)

b. Use the limiting reagent to calculate the moles of product (FeBr3) formed. (3)

c. Calculate the moles of the excess reagent which do not react. (2)