Stoichiometry

Review

1. Zinc metal (65.38 g/mol) is dropped into a solution of hydrochloric acid (36.46 g/mol) producing hydrogen gas (2.02 g/mol) and zinc chloride (136.28 g/mol).

Zn + 2 HCl ZnCl2 + H₂

a. How many moles of hydrogen gas are produced by 30.00 mol of hydrochloric acid?

b. How many moles of hydrochloric acid are required for every 4.50 mol of zinc?

c. If 1000 grams of zinc are reacted, how many grams of zinc chloride are produced? d. For every 1000 grams of zinc used, how many moles of hydrogen gas are produced?

2. Predict the mass of hydrogen gas (2.02 g/mol) produced when 100 grams of aluminum (26.98 g/mol) reacts in a single replacement reaction with sulfuric acid (98.08 g/mol).

3. A piece of zinc (65.38 g/mol) is dropped into a solution of lead (II) chloride (207.09 g/mol) to produce lead metal (207.19 g/mol) and a solution of zinc chloride. The lead metal is recovered by filtration and dried overnight.

The following data was recorded:

• initial mass of zinc ____________ 27.538 grams
• final mass of zinc _____________ 21.000 grams
• mass of filter paper ___________ 0.920 grams
• mass of filter paper and lead ____ 21.000 grams

a. Write the balanced equation for this reaction above.

b. Using the data above, calculate the theoretical yield of lead metal.

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

4. Calculate the moles of precipitate produced when 32.80 grams of sodium phosphate (163.94 g/mol) reacts with calcium nitrate in a double replacement reaction.

5. Suppose that 300 grams of magnesium metal (24.32 g/mol) reacts with 300 grams of oxygen gas (32.00 g/mol). Calculate the mass of magnesium oxide (40.31 g/mol) which should be produced.

6. Aluminum reacts with chlorine to produce aluminum chloride. Suppose that you have 16.0 mol of aluminum and 20.4 mol of chlorine.

2 Al (16.0 mol) + 3 Cl₂ (20.4 mol) 2 AlCl₃

a. Identify the limiting reagent. Please show your work.

b. Use the limiting reagent to calculate the mass of product (AlCl3) formed.

c. How many moles of excess reagent are there? How many grams?