Equation Problems

Skill Developing Problems

What is/are the product(s) containing carbon when methane, CH4, is burned in the air?
Hint . . .CO2

Generalization:Combustion of C containing compounds converts all C to CO2.

Use the common sense method to find the molecular formula for hydrogen sulfide, whose molecular weight is 34.1. (Atomic weight, H, 1.008; S, 32.066) Hint . . .H2S

Generalization:Sulfur and oxygen are group 6 elements, and they form H2O and H2S.

When 30.0 g of Al (atomic weight 27.0) is heated in oxygen (atomic mass 16.0), an aluminum oxide, Al2O3, is formed. How much oxide should be obtained. Hint . . .56.7 g A Variation:How much (in g) oxygen is required?

When KClO3 is heated, it decomposes to give solid KCl and oxygen gas. If 0.500 mol O2 is collected, how many grams of KCl should be obtained? (Atomic wt: K, 39.098; Cl, 35.453) Hint . . .24.9 g Method suggestion:

For the reaction:
2 KClO3 = 2 KCl + 3 O2 the formulation suggestion is: 2 mole KCl 74.6 g KCl
0.50 mol O2 ------------ ------------ = ??.? g KCl
3 mol O2 1 mol KCl

A solution containing pure BaCl2 is treated with excess amounts of H2SO4, and the precipitate BaSO4 is collected and dried. If 13.2 g of BaSO4 are collected, how many moles of Cl- ions are left in the solution?Atomic wt: H, 1.008; O, 16.00; S, 32.06; Cl, 35.45; Ba, 137.33. Hint . . .0.113 mol

Variations:How much (in g) BaCl2 is present in the solution?How much silver nitrate is required to precipitate all the chloride ions?

The reaction is:
BaCl2 + H2SO4 = BaSO4 + 2 H+ + 2 Cl-. 0.0566 mole of Ba correspond to 0.113 mol of Cl- in BaCl2. Method Suggestion 1 mol BaSO4 2 mol Cl-
13.2 g ----------- ----------- = 0.113 mol
233.39 g 1 mol BaSO4

A power plant burns coal, and this process is equivalent to burning 999 kg of sulfur a day. How many kg of SO2 is emitted per day if the power plant does not have pollution control devices to recover the sulfur? Atomic wt: C, 12.00; O, 16.00; S, 32.06. Hint . . .1998 kg

Further consideration:The molecular weight of SO2 is about twice the atomic weight of S. Thus the weight of SO2 is twice that of S. Variations: How much (in mole and L) SO2 is generated per day?If all SO2 is converted to H2SO4, how much (in mol and kg) sulfuric acid is produced? (3055 kg)

How many moles of water will be formed when one mole of propane C3H8 is burned in an excess amount of air? Hint . . .4 molesC3H8 + 5 O2 = 3 CO2 + 4 H2O Skill:Work out a balanced reaction equation.

Variations:How many grams of water will be produced?How many moles of CO2 will be produced?

A mixture containing Na2SO4, but no other sulfate, is analyzed by precipitation with BaCl2. A 2.37 g mixture sample gave a 2.57 g BaSO4 precipitate.

What is the percentage of Na2SO4 in the mixture? Hint . . .66.0 %

Skill:The problem illustrates a strategy for chemical analysis.

When 2.33 g of CaCl2 and Ca(NO3)2 mixture gives 2.22 g of AgCl when Ag(NO3) is used as a reagent to precipitate the chloride Cl- ions. What is the percentage of CaCl2 in the mixture?

Atomic wt: N, 14.0; O, 16.0; Cl, 35.5; Ca, 40.1; Ag, 107.9. Hint . . .36.9 %

Skill:This problem also illustrates a strategy for chemical analysis.
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