Name: Chemistry: The Central Science
Author: Brown
ISBN: 9780134414232

Ch.4 - Reactions in Aqueous Solution

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Brown 14th Edition

Ch.4 - Reactions in Aqueous Solution

Problem 89

A 0.5895-g sample of impure magnesium hydroxide is dissolved in 100.0 mL of 0.2050 M HCl solution. The excess acid then needs 19.85 mL of 0.1020 M NaOH for neutralization. Calculate the percentage by mass of magnesium hydroxide in the sample, assuming that it is the only substance reacting with the HCl solution.

Problem 90

A 1.248-g sample of limestone rock is pulverized and then treated with 30.00 mL of 1.035 M HCl solution. The excess acid then requires 11.56 mL of 1.010 M NaOH for neutralization. Calculate the percentage by mass of calcium carbonate in the rock, assuming that it is the only substance reacting with the HCl solution.

Problem 91a,b

Uranium hexafluoride, UF₆, is processed to produce fuel for nuclear reactors and nuclear weapons. UF₆ can be produced in a two-step reaction. Solid uranium (IV) oxide, UO₂, is first made to react with hydrofluoric acid (HF) solution to form solid UF₄ with water as a by-product. UF₄ further reacts with fluorine gas to form UF6. (a) Write the balanced molecular equations for the conversion of UO₂ into UF₄ and the conversion of UF₄ to UF₆. (b) Which step is an acid-base reaction?

Problem 92b

The accompanying photo shows the reaction between a solution of Cd(NO₃)₂ and one of Na₂S. (b) What ions remain in solution?

Problem 94

You choose to investigate some of the solubility guidelines for two ions not listed in Table 4.1, the chromate ion (CrO₄²⁻) and the oxalate ion (C₂O₄²⁻). You are given 0.01 M solutions (A, B, C, D) of four water-soluble salts: When these solutions are mixed, the following observations are made:

(a) Write a net ionic equation for the reaction that occurs in the first experiment. (b) Identify the precipitate formed in the first experiment. (c) Write a net ionic equation for the reaction that occurs in the third experiment. (d) Identify the precipitate formed in the third experiment. (e) Write a net ionic equation for the reaction that occurs in the fourth experiment. (f) Identify the precipitate formed in the fourth experiment. (g) Write a net ionic equation for the reaction that occurs in the fifth experiment. (h) Identify the precipitate formed in the fifth experiment. (i) Write a net ionic equation for the reaction that occurs in the sixth experiment. (j) Identify the precipitate formed in the sixth experiment.

Problem 95

Antacids are often used to relieve pain and promote healing in the treatment of mild ulcers. Write balanced net ionic equations for the reactions between the aqueous HCl in the stomach and each of the following substances used in various antacids: (a) Al(OH)₃(s) (b) Mg(OH)₂(s) (c) MgCO₃(s) (d) NaAl(CO₃)(OH)₂(s) (e) CaCO₃(s).

Problem 96a

The commercial production of nitric acid involves the following chemical reactions:

4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g)

2 NO(g) + O₂(g) → 2 NO₂(g)

3 NO₂(g) + H₂O(l) → 2 HNO₃(aq) + NO(g)

(a) Which of these reactions are redox reactions?

Problem 96b

The commercial production of nitric acid involves the following chemical reactions:

4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g)

2 NO(g) + O₂(g) → 2 NO₂(g)

3 NO₂(g) + H₂O(l) → 2 HNO₃(aq) + NO(g)

(b) Identify the element undergoing oxidation and the element undergoing reduction.

Problem 96c

The commercial production of nitric acid involves the following chemical reactions:

4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g)

2 NO(g) + O₂(g) → 2 NO₂(g)

3 NO₂(g) + H₂O(l) → 2 HNO₃(aq) + NO(g)

(c) How many grams of ammonia must you start with to make 1000.0 L of a 0.150 M aqueous solution of nitric acid? Assume all the reactions give 100% yield.

Problem 97a

Consider the following reagents: zinc, copper, mercury (density 13.6 g/mL), silver nitrate solution, nitric acid solution. (a) Given a 500-mL Erlenmeyer flask and a balloon, can you combine two or more of the foregoing reagents to initiate a chemical reaction that will inflate the balloon? Write a balanced chemical equation to represent this process. What is the identity of the substance that inflates the balloon?

Problem 98

A 100.0-g sample of a certain bronze is 90.0% copper by mass and 10.0% tin. Which metal can be called the solvent, and which the solute?

Problem 98b

Bronze is a solid solution of Cu(s) and Sn(s); solutions of metals like this that are solids are called alloys. There is a range of compositions over which the solution is considered a bronze. Bronzes are stronger and harder than either copper or tin alone. (b) Based on part (a), calculate the concentration of the solute metal in the alloy in units of molarity, assuming a density of 7.9 g/cm³.

Problem 98c

Bronze is a solid solution of Cu(s) and Sn(s); solutions of metals like this that are solids are called alloys. There is a range of compositions over which the solution is considered a bronze. Bronzes are stronger and harder than either copper or tin alone. (c) Suggest a reaction that you could do to remove all the tin from this bronze to leave a pure copper sample. Justify your reasoning.

Problem 100c

Neurotransmitters are molecules that are released by nerve cells to other cells in our bodies, and are needed for muscle motion, thinking, feeling, and memory. Dopamine is a common neurotransmitter in the human brain. (c) Experiments with rats show that if rats are dosed with 3.0 mg/kg of cocaine (that is, 3.0 mg cocaine per kg of animal mass), the concentration of dopamine in their brains increases by 0.75 mM after 60 seconds. Calculate how many molecules of dopamine would be produced in a rat (average brain volume 5.00 mm3) after 60 seconds of a 3.0 mg/kg dose of cocaine.

Problem 101b

Hard water contains Ca2+, Mg2+, and Fe2+, which interfere with the action of soap and leave an insoluble coating on the insides of containers and pipes when heated. Water softeners replace these ions with Na+. Keep in mind that charge balance must be maintained. (b) If the sodium is added to the water softener in the form of NaCl, how many grams of sodium chloride are needed?

Problem 102a

Citric acid, C6H8O7, is a triprotic acid. It occurs naturally in citrus fruits like lemons and has applications in food flavouring and preservatives. A solution containing an unknown concentration of the acid is titrated with KOH. It requires 23.20 mL of 0.500 M KOH solution to titrate all three acidic protons in 100.00 mL of the citric acid solution. Write a balanced net ionic equation for the neutralization reaction.

Problem 102b

Citric acid, C6H8O7, is a triprotic acid. It occurs naturally in citrus fruits like lemons and has applications in food flavouring and preservatives. A solution containing an unknown concentration of the acid is titrated with KOH. It requires 23.20 mL of 0.500 M KOH solution to titrate all three acidic protons in 100.00 mL of the citric acid solution. Calculate the molarity of the citric acid solution.

Problem 103

(c) If 18.65 mL of the caesium hydroxide solution was needed to neutralize a 42.3 mL aliquot of the hydroiodic acid solution, what is the concentration (molarity) of the acid?

Problem 105a

Suppose you have 3.00 g of powdered zinc metal, 3.00g of powdered silver metal and 500.0 mL of a 0.2 M copper(II) nitrate solution. (a) Which metal will react with the copper(II) nitrate solution?

Problem 105b

Suppose you have 3.00 g of powdered zinc metal, 3.00g of powdered silver metal and 500.0 mL of a 0.2 M copper(II) nitrate solution. (b) What is the net ionic equation that describes this reaction?

Problem 106a

(a) By titration, 15.0 mL of 0.1008 M sodium hydroxide is needed to neutralize a 0.2053-g sample of a weak acid. What is the molar mass of the acid if it is monoprotic?

Problem 106b

(b) An elemental analysis of the acid indicates that it is composed of 5.89% H, 70.6% C, and 23.5% O by mass. What is its molecular formula?

Problem 107

The discovery of hafnium, element number 72, provided a controversial episode in chemistry. G. Urbain, a French chemist, claimed in 1911 to have isolated an element number 72 from a sample of rare earth (elements 58–71) compounds. However, Niels Bohr believed that hafnium was more likely to be found along with zirconium than with the rare earths. D. Coster and G. von Hevesy, working in Bohr's laboratory in Copenhagen, showed in 1922 that element 72 was present in a sample of Norwegian zircon, an ore of zirconium. (The name hafnium comes from the Latin name for Copenhagen, Hafnia). (c) Solid zirconium dioxide, ZrO2, reacts with chlorine gas in the presence of carbon. The products of the reaction are ZrCl4 and two gases, CO2 and CO in the ratio 1:2. Write a balanced chemical equation for the reaction.

Problem 108

A fertilizer railroad car carrying 129,840 L of commercial aqueous ammonia (30% ammonia by mass) tips over and spills. The density of the aqueous ammonia solution is 0.88 g/cm³. What mass of citric acid, C₆H₈O₇ (which contains three acidic protons), is required to neutralize the spill?

Problem 109c

A sample of 8.69 g of Zn(OH)₂ is added to 155.0 mL of 0.750 M H₂SO₄. (c) How many moles of Zn(OH)₂, H₂SO₄, ZnSO₄ are present after the reaction is complete?

Problem 110a

In 2014, a major chemical leak at a facility in West Virginia released 28,390 L of MCHM (4-methylcyclohexylmethanol, C8H16O) into the Elk River. The density of MCHM is 0.9074 g/mL. (a) Calculate the initial molarity of MCHM in the river, assuming that the first part of the river is 2.00 m deep, 90.0 m wide, and 90.0 m long.

Problem 111

Ritalin is the trade name of a drug, methylphenidate, used to treat attention-deficit/hyperactivity disorder in young adults. The chemical structure of methylphenidate is (c) Ritalin has a half-life of 3 hours in the blood, which means that after 3 hours the concentration in the blood has decreased by half of its initial value. For the man in part (b), what is the concentration of Ritalin in his blood after 6 hours?

Problem 112

A 3.50 g of an alloy which contains only lead and tin is dissolved in hot HNO3. Excess sulfuric acid is added to this solution and 1.57 g of PbSO4(s) is obtained. (a) Write the net ionic equation for the formation of PbSO4.

Problem 113a

The arsenic in a 1.22-g sample of a pesticide was converted to AsO₄^3- by suitable chemical treatment. It was then titrated using Ag⁺ to form Ag₃AsO₄ as a precipitate. (a) What is the oxidation state of As in AsO₄^3-?

Problem 113b

The arsenic in a 1.22-g sample of a pesticide was converted to AsO₄^3- by suitable chemical treatment. It was then titrated using Ag⁺ to form Ag₃AsO₄ as a precipitate. (b) Name Ag₃AsO₄ by analogy to the corresponding compound containing phosphorus in place of arsenic.