1. Many important metals occur as sulfide, arsenide, and antimonide minerals, especially in the Sudbury mineral complex. The first step in processing these ores involves "roasting" the ore in air to produce the metal or metal oxide, along with nonmetal oxides that can be serious pollutants if not trapped.

Suppose that you roast 1.00 kg of the mineral shandite, Ni₃Pb₂S₂. The balanced equation for the reaction is:

2Ni₃Pb₂S₂ + 9O₂ → 6NiO + 4 PbO + 4SO₂

(a) How many kg of NiO can be produced?

(b) How many kg of the pollutant PbO can be produced?

(c) How many liters of air at 25°C are required for roasting? Assume that air contains 23% O₂ by mass, and that the density of air at 25°C is 1.2 g/L.

Molar masses: Ni₃Pb₂S₂ 654.6 g/mol      NiO 74.69 g/mol     PbO 223.20 g/mol

2. A mixture of Na₂SO₄ and its hydrate Na₂SO₄•10H₂O has a mass of 1.8092 g. After heating to drive off all the water, the mass is only 1.6526 g. What is the weight percentage of Na₂SO₄•10H₂O in the original mixture?

Report your answer to 4 significant figures.

Molar masses: Na₂SO₄ 142.04 g/mol; Na₂SO₄•10H₂O 322.19 g/mol.

3. MnCl₂ reacts with AgNO₃ in aqueous solutions to produce a precipitate of AgCl that can be filtered and weighed. The balanced equation for the reaction is:

MnCl₂ (aq) + 2 AgNO₃ (aq) → 2 AgCl (s) + Mn(NO₃)₂ (aq)

Suppose you have a mixture that contains MnCl₂, plus other compounds that do not react with AgNO₃. If 0.4033 g of the mixture yields 0.6589 g of AgCl, what is the percentage of MnCl₂ in the mixture?

Molar masses: MnCl₂ 125.84 g/mol AgCl 143.32 g/mol

4. Potassium perchlorate is used in the production of fireworks and explosives. It is made in a two-step reaction. First, potassium hypochlorite disproportionates to potassium chloride and potassium chlorate. Then the potassium chlorate disproportionates again to form potassium perchlorate and potassium chloride. The equations are:

3 KClO (aq) → 2 KCl (aq) + KClO₃ (aq)
4 KClO₃ (aq) → 3 KClO₄ (s) + KCl (aq)

What mass of KClO4 (in kg) can be obtained from 3.40 kg of KClO when these reactions are carried out? Molar masses (g/mol): KClO 90.55 KClO₄ 138.55

5. An organic compound containing only C, H, and possibly O was subjected to combustion analysis. A sample weighing 0.5567 g yielded 0.941 g CO₂ and 0.385 g H₂O. What is the empirical formula of the compound?

6. For the complete redox reaction given here, (a) break down each reaction into its half reactions; (b) identify the oxidizing agent; and (c) identify the reducing agent.

O₂ + 2Zn → 2ZnO

7. Give the oxidation number of nitrogen in each of the following compounds or ions:

(a) Mg(NO₂)₂

(b) Li₃N
(c) N₂H₂
(d) N₂O₃
(e) NO^3-

8.

Consider the following net ionic equation for a redox reaction:
5 H₂O₂ + 2 MnO^4- + 6 H⁺ → 5O₂ + 2 Mn²⁺ + 8H₂O

(a) Which reactant gets oxidized?

(b) Which reactant gets reduced?

(c) Which reactant is the oxidizing agent? (d) Which reactant is the reducing agent?