STOICHIOMETRY REVIEW

Solve the following problems on a separate sheet of paper. Show all of your work and be sure to round your final answer to the correct number of significant figures.

  1. Calculate the number of moles of potassium chlorate (KClO3) that must decompose to produce 1.80 moles of oxygen gas.

KClO3  KCl + O2

  1. How many grams of iron (III) chloride are formed when 111.7 g of iron react according to the following equation?

Fe + Cl2  FeCl3

  1. Calculate the liters of nitrogen dioxide gas formed when 1.22 moles of ammonia (NH3) react completely at STP.

NH3 + O2  NO2 + H2O

  1. How many liters of oxygen gas can be produced if 15.0 g of mercury(II) oxide are heated according to the following equation? The density of oxygen is 1.429 g/L.

HgO  Hg + O2

  1. If 75.0 mL of 0.100 M mercury(II) nitrate [ Hg(NO3)2 ] are reacted with excess sodium iodide (NaI), how many grams of mercury(II) iodide (HgI2) are formed?

NaI + Hg(NO3)2  HgI2 + NaNO3

  1. What volume of 0.60 M copper(II) sulfate (CuSO4) will react with 45.0 mL of 1.50 M sodium hydroxide (NaOH)?

CuSO4 + NaOH  Cu(OH)2 + Na2SO4

7. If 100.0 g of zinc metal and 100.0 g of copper(II) nitrate [Cu(NO3)2] react, which is the limiting reactant and how many grams of copper metal will be produced?

Zn + Cu(NO3)2  Cu + Zn(NO3)2

  1. What is the limiting reactant when 15.5 g of aluminum are reacted with 46.7 g of chlorine gas by way of the following equation? How many grams of excess reactant remain unreacted?

Al + Cl2  AlCl3

  1. For each of the following unbalanced reactions, suppose exactly 5.00 g of each reactant is taken. Determine which reactant is limiting, and also determine what mass of the excess reactant will remain after the limiting reactant is consumed.
  1. Na2B4O7 + H2SO4 + H2O  H3BO3 + Na2SO4
  2. CaC2 + H2O  Ca(OH)2 + C2H2
  3. NaCl + H2SO4  HCl + Na2SO4
  4. SiO2 + C  Si + CO
  1. If steel wool (iron) is heated until it glows and is placed in a bottle containing pure oxygen, the iron reacts spectacularly to produce iron(III) oxide.

4Fe + 3O2  2Fe2O3

If 1.25 g of iron is heated and placed in a bottle containing 0.0204 mol of oxygen gas, what mass of iron(III) oxide is produced? Hint: which reactant is limiting?

  1. A student calculated the theoretical yield of barium sulfate in a precipitation reaction to be 1.352 g. When she filtered, dried, and weighed her precipitate, however, her yield was only 1.279 g. Calculate the student’s percent yield.
  1. Although they were formerly called the inert gases, at least the heavier elements of Group 8 do form relatively stable compounds. For example, xenon combines directly with elemental fluorine at elevated temperatures in the presence of a nickel catalyst.

Xe + 2F2  XeF4

What is the theoretical mass of xenon tetrafluoride that should form when 130. g of xenon is reacted with excess fluorine? What is the percent yield if only 145 g of XeF4 is actually isolated?

13. Although we usually think of substances as “burning” only in oxygen gas, the process of rapid oxidation to produce a flame may also take place in other strongly oxidizing gases. For example, when iron is heated and placed in pure chlorine gas, the iron “burns” according to the following reaction:

2Fe + 3Cl2  2FeCl3

How many grams of iron(III) chloride result when 15.5 g of iron is reacted with an excess of chlorine gas?

14. The reaction given below has a percent yield of 65%. How many grams of NH3 would be produced by reacting 2.44 g of N2 gas?

N2 + 3H2  2NH3