Exercises

Consider molecular, complete ionic, and net ionic equations.

(a) What is the difference between these types of equations?

(b) In what circumstance would the complete and net ionic equations for a reaction be identical?

Balance the following equations:

(a) $\text{Ag}(s)+{\text{H}}_2\text{S}(g)+{\text{O}}_2(g)⟶{\text{Ag}}_2\text{S}(s)+{\text{H}}_2\text{O}(l)$

(b) ${\text{P}}_4(s)+{\text{O}}_2(g)⟶{\text{P}}_4{\text{O}}_{10}(s)$

(c) $\text{Pb}(s)+{\text{H}}_2\text{O}(l)+{\text{O}}_2(g)⟶{\text{Pb(OH)}}_2(s)$

(d) $\text{Fe}(s)+{\text{H}}_2\text{O}(l)⟶{\text{Fe}}_3{\text{O}}_4(s)+{\text{H}}_2(g)$

(e) ${\text{Sc}}_2{\text{O}}_3(s)+{\text{SO}}_3(l)⟶{\text{Sc}}_{\text{2}}({\text{S}{\text{O}}_4)}_3(s)$

(f) ${\text{Ca}}_{\text{3}}({\text{P}{\text{O}}_4)}_2(aq)+{\text{H}}_3{\text{PO}}_4(aq)⟶\text{Ca}{({\text{H}}_2{\text{PO}}_4)}_2(aq)$

(g) $\text{Al}(s)+{\text{H}}_2{\text{SO}}_4(aq)⟶{\text{Al}}_{\text{2}}({\text{S}{\text{O}}_4)}_3(s)+{\text{H}}_2(g)$

(h) ${\text{TiCl}}_4(s)+{\text{H}}_2\text{O}(g)⟶{\text{TiO}}_2(s)+\text{HCl}(g)$

Write a balanced equation describing each of the following chemical reactions.

(a) Solid potassium chlorate, KClO₃, decomposes to form solid potassium chloride and diatomic oxygen gas.

(b) Solid aluminum metal reacts with solid diatomic iodine to form solid Al₂I₆.

(c) When solid sodium chloride is added to aqueous sulfuric acid, hydrogen chloride gas and aqueous sodium sulfate are produced.

(d) Aqueous solutions of phosphoric acid and potassium hydroxide react to produce aqueous potassium dihydrogen phosphate and liquid water.

Fill in the blank with a single chemical formula for a covalent compound that will balance the equation:

A novel process for obtaining magnesium from sea water involves several reactions. Write a balanced chemical equation for each step of the process.

(a) The first step is the decomposition of solid calcium carbonate from seashells to form solid calcium oxide and gaseous carbon dioxide.

(b) The second step is the formation of solid calcium hydroxide as the only product from the reaction of the solid calcium oxide with liquid water.

(c) Solid calcium hydroxide is then added to the seawater, reacting with dissolved magnesium chloride to yield solid magnesium hydroxide and aqueous calcium chloride.

(d) The solid magnesium hydroxide is added to a hydrochloric acid solution, producing dissolved magnesium chloride and liquid water.

(e) Finally, the magnesium chloride is melted and electrolyzed to yield liquid magnesium metal and diatomic chlorine gas.

Use the following equations to answer the next four questions:

i. ${\text{H}}_2\text{O}(s)⟶{\text{H}}_2\text{O}(l)$

ii. ${\text{Na}}^{\text{+}}(aq)+{\text{Cl}}^{\text{−}}(\text{aq})+{\text{Ag}}^{\text{+}}(aq)+{\text{NO}}_3{}^{\text{−}}(aq)⟶\text{AgCl}(s)+{\text{Na}}^{\text{+}}(aq)+{\text{NO}}_3{}^{\text{−}}(aq)$

iii. ${\text{CH}}_3\text{OH}(g)+{\text{O}}_2(g)⟶{\text{CO}}_2(g)+{\text{H}}_2\text{O}(g)$

iv. $2{\text{H}}_2\text{O}(l)⟶2{\text{H}}_2(g)+{\text{O}}_2(g)$

v. ${\text{H}}^{\text{+}}(aq)+{\text{OH}}^{\text{−}}(aq)⟶{\text{H}}_2\text{O}(l)$

(a) Which equation describes a physical change?

(b) Which equation identifies the reactants and products of a combustion reaction?

(c) Which equation is not balanced?

(d) Which is a net ionic equation?

Indicate what type, or types, of reaction each of the following represents:

(a) ${\text{H}}_2\text{O}(g)+\text{C}(s)⟶\text{CO}(g)+{\text{H}}_2(g)$

(b) ${\text{2KClO}}_3(s)⟶2\text{KCl}(s)+3{\text{O}}_2(g)$

(c) $\text{Al}{\text{(OH)}}_3(aq)+3\text{HCl}(aq)⟶{\text{AlCl}}_3(aq)+3{\text{H}}_2\text{O}(l)$

(d) $\text{Pb}{({\text{NO}}_3)}_2(aq)+{\text{H}}_2{\text{SO}}_4(aq)⟶{\text{PbSO}}_4(s)+2{\text{HNO}}_3(aq)$

Determine the oxidation states of the elements in the following compounds:

(a) NaI

(b) GdCl₃

(c) LiNO₃

(d) H₂Se

(e) Mg₂Si

(f) RbO₂, rubidium superoxide

(g) HF

Determine the oxidation states of the elements in the compounds listed. None of the oxygen-containing compounds are peroxides or superoxides.

(a) H₂SO₄

(b) Ca(OH)₂

(c) BrOH

(d) ClNO₂

(e) TiCl₄

(f) NaH

Identify the atoms that are oxidized and reduced, the change in oxidation state for each, and the oxidizing and reducing agents in each of the following equations:

(a) $\text{Mg}(s)+{\text{NiCl}}_2(aq)⟶{\text{MgCl}}_2(aq)+\text{Ni}(s)$

(b) ${\text{PCl}}_3(l)+{\text{Cl}}_2(g)⟶{\text{PCl}}_5(s)$

(c) ${\text{C}}_2{\text{H}}_4(g)+3{\text{O}}_2(g)⟶2{\text{CO}}_2(g)+2{\text{H}}_2\text{O}(g)$

(d) $\text{Zn}(s)+{\text{H}}_2{\text{SO}}_4(aq)⟶{\text{ZnSO}}_4(aq)+{\text{H}}_2(g)$

(e) $2{\text{K}}_2{\text{S}}_2{\text{O}}_3(s)+{\text{I}}_2(s)⟶{\text{K}}_2{\text{S}}_4{\text{O}}_6(s)+2\text{KI}(s)$

(f) $3\text{Cu}(s)+8{\text{HNO}}_3(aq)⟶3\text{Cu}{({\text{NO}}_3)}_2(aq)+2\text{NO}(g)+4{\text{H}}_2\text{O}(l)$

Complete and balance the following acid-base equations:

(a) A solution of HClO₄ is added to a solution of LiOH.

(b) Aqueous H₂SO₄ reacts with NaOH.

(c) Ba(OH)₂ reacts with HF gas.

Complete and balance the following oxidation-reduction reactions, which give the highest possible oxidation state for the oxidized atoms.

(a) $\text{K}(s)+{\text{H}}_2\text{O}(l)⟶$

(b) $\text{Ba}(s)+\text{HBr}(aq)⟶$

(c) $\text{Sn}(s)+{\text{I}}_2(s)⟶$

When heated to 700–800 °C, diamonds, which are pure carbon, are oxidized by atmospheric oxygen. (They burn!) Write the balanced equation for this reaction.

Write the molecular, total ionic, and net ionic equations for the following reactions:

(a) $\text{Ca}{\text{(OH)}}_2(aq)+{\text{HC}}_2{\text{H}}_3{\text{O}}_2(aq)⟶$

(b) ${\text{H}}_3{\text{PO}}_4(aq)+{\text{CaCl}}_2(aq)⟶$

In a common experiment in the general chemistry laboratory, magnesium metal is heated in air to produce MgO. MgO is a white solid, but in these experiments it often looks gray, due to small amounts of Mg₃N₂, a compound formed as some of the magnesium reacts with nitrogen. Write a balanced equation for each reaction.

Calcium propionate is sometimes added to bread to retard spoilage. This compound can be prepared by the reaction of calcium carbonate, CaCO₃, with propionic acid, C₂H₅CO₂H, which has properties similar to those of acetic acid. Write the balanced equation for the formation of calcium propionate.

Copper(II) sulfide is oxidized by molecular oxygen to produce gaseous sulfur trioxide and solid copper(II) oxide. The gaseous product then reacts with liquid water to produce liquid hydrogen sulfate as the only product. Write the two equations which represent these reactions.

Calcium cyclamate Ca(C₆H₁₁NHSO₃)₂ is an artificial sweetener used in many countries around the world but is banned in the United States. It can be purified industrially by converting it to the barium salt through reaction of the acid C₆H₁₁NHSO₃H with barium carbonate, treatment with sulfuric acid (barium sulfate is very insoluble), and then neutralization with calcium hydroxide. Write the balanced equations for these reactions.

Complete and balance each of the following half-reactions (steps 2–5 in half-reaction method):

(a) ${\text{Cr}}^{\mathrm{2+}}(aq)⟶{\text{Cr}}^{\mathrm{3+}}(aq)$

(b) $\text{Hg}(l)+{\text{Br}}^{\text{−}}(aq)⟶{\text{HgBr}}_4{}^{\mathrm{2-}}(aq)$

(c) $\text{ZnS}(s)⟶\text{Zn}(s)+{\text{S}}^{\mathrm{2-}}(aq)$

(d) ${\text{H}}_2(g)⟶{\text{H}}_2\text{O}(l)(\text{in basic solution})$

(e) ${\text{H}}_2(g)⟶{\text{H}}_3{\text{O}}^{\text{+}}(aq)(\text{in acidic solution})$

(f) ${\text{NO}}_3{}^{\text{−}}(aq)⟶{\text{HNO}}_2(aq)\text{(in acidic solution)}$

(g) ${\text{MnO}}_2(s)⟶{\text{MnO}}_4{}^{\text{−}}(aq)\text{(in basic solution)}$

(h) ${\text{Cl}}^{\text{−}}(aq)⟶{\text{ClO}}_3{}^{\text{−}}(aq)\text{(in acidic solution)}$

Balance each of the following equations according to the half-reaction method:

(a) $\text{Zn}(s)+{\text{NO}}_3{}^{\text{−}}(aq)⟶{\text{Zn}}^{\mathrm{2+}}(aq)+{\text{N}}_2(g)\text{(in acid)}$

(b) $\text{Zn}(s)+{\text{NO}}_3{}^{\text{−}}(aq)⟶{\text{Zn}}^{\mathrm{2+}}(aq)+{\text{NH}}_3(aq)\text{(in base)}$

(c) $\text{CuS}(s)+{\text{NO}}_3{}^{\text{−}}(aq)⟶{\text{Cu}}^{\mathrm{2+}}(aq)+\text{S}(s)+\text{NO}(g)\text{(in acid)}$

(d) ${\text{NH}}_3(aq)+{\text{O}}_2(g)⟶{\text{NO}}_2(g)\text{(gas phase)}$

(e) ${\text{Cl}}_2(g)+{\text{OH}}^{\text{−}}(aq)⟶{\text{Cl}}^{\text{−}}(aq)+{\text{ClO}}_3{}^{\text{−}}(aq)\text{(in base)}$

(f) ${\text{H}}_2{\text{O}}_2(aq)+{\text{MnO}}_4{}^{\text{−}}(aq)⟶{\text{Mn}}^{\mathrm{2+}}(aq)+{\text{O}}_2(g)\text{(in acid)}$

(g) ${\text{NO}}_2(g)⟶{\text{NO}}_3{}^{\text{−}}(aq)+{\text{NO}}_2{}^{\text{−}}(aq)\text{(in base)}$

(h) ${\text{Fe}}^{\mathrm{3+}}(aq)+{\text{I}}^{\text{−}}(aq)⟶{\text{Fe}}^{\mathrm{2+}}(aq)+{\text{I}}_2(aq)$

Write the balanced equation, then outline the steps necessary to determine the information requested in each of the following:

(a) The number of moles and the mass of chlorine, Cl₂, required to react with 10.0 g of sodium metal, Na, to produce sodium chloride, NaCl.

(b) The number of moles and the mass of oxygen formed by the decomposition of 1.252 g of mercury(II) oxide.

(c) The number of moles and the mass of sodium nitrate, NaNO₃, required to produce 128 g of oxygen. (NaNO₂ is the other product.)

(d) The number of moles and the mass of carbon dioxide formed by the combustion of 20.0 kg of carbon in an excess of oxygen.

(e) The number of moles and the mass of copper(II) carbonate needed to produce 1.500 kg of copper(II) oxide. (CO₂ is the other product.)

(f)

Write the balanced equation, then outline the steps necessary to determine the information requested in each of the following:

(a) The number of moles and the mass of Mg required to react with 5.00 g of HCl and produce MgCl₂ and H₂.

(b) The number of moles and the mass of oxygen formed by the decomposition of 1.252 g of silver(I) oxide.

(c) The number of moles and the mass of magnesium carbonate, MgCO₃, required to produce 283 g of carbon dioxide. (MgO is the other product.)

(d) The number of moles and the mass of water formed by the combustion of 20.0 kg of acetylene, C₂H₂, in an excess of oxygen.

(e) The number of moles and the mass of barium peroxide, BaO₂, needed to produce 2.500 kg of barium oxide, BaO (O₂ is the other product.)

(f)

H₂ is produced by the reaction of 118.5 mL of a 0.8775-M solution of H₃PO₄ according to the following equation: $2\text{Cr}+2{\text{H}}_3{\text{PO}}_4⟶3{\text{H}}_2+2{\text{CrPO}}_4.$

(a) Outline the steps necessary to determine the number of moles and mass of H₂.

(b) Perform the calculations outlined.

I₂ is produced by the reaction of 0.4235 mol of CuCl₂ according to the following equation: $2{\text{CuCl}}_2+4\text{KI}⟶2\text{CuI}+4\text{KCl}+{\text{I}}_2.$

(a) How many molecules of I₂ are produced?

(b) What mass of I₂ is produced?

What mass of silver oxide, Ag₂O, is required to produce 25.0 g of silver sulfadiazine, AgC₁₀H₉N₄SO₂, from the reaction of silver oxide and sulfadiazine?
$2{\text{C}}_{10}{\text{H}}_{10}{\text{N}}_4{\text{SO}}_2+{\text{Ag}}_2\text{O}⟶2{\text{AgC}}_{10}{\text{H}}_9{\text{N}}_4{\text{SO}}_2+{\text{H}}_2\text{O}$

Automotive air bags inflate when a sample of sodium azide, NaN₃, is very rapidly decomposed.
$2{\text{NaN}}_3(s)⟶2\text{Na}(s)+3{\text{N}}_2(g)$
What mass of sodium azide is required to produce 2.6 ft³ (73.6 L) of nitrogen gas with a density of 1.25 g/L?

In an accident, a solution containing 2.5 kg of nitric acid was spilled. Two kilograms of Na₂CO₃ was quickly spread on the area and CO₂ was released by the reaction. Was sufficient Na₂CO₃ used to neutralize all of the acid?

What volume of 0.750 M hydrochloric acid solution can be prepared from the HCl produced by the reaction of 25.0 g of NaCl with excess sulfuric acid?
$\text{NaCl}(s)+{\text{H}}_2{\text{SO}}_4(l)⟶\text{HCl}(g)+{\text{NaHSO}}_4(s)$

A mordant is a substance that combines with a dye to produce a stable fixed color in a dyed fabric. Calcium acetate is used as a mordant. It is prepared by the reaction of acetic acid with calcium hydroxide.
$2{\text{CH}}_3{\text{CO}}_2\text{H}+\text{Ca}{\text{(OH)}}_2⟶\text{Ca}{({\text{CH}}_3{\text{CO}}_2)}_2+2{\text{H}}_2\text{O}$

What mass of Ca(OH)₂ is required to react with the acetic acid in 25.0 mL of a solution having a density of 1.065 g/mL and containing 58.0% acetic acid by mass?

The following quantities are placed in a container: 1.5 $\times$ 10²⁴ atoms of hydrogen, 1.0 mol of sulfur, and 88.0 g of diatomic oxygen.

(a) What is the total mass in grams for the collection of all three elements?

(b) What is the total number of moles of atoms for the three elements?

(c) If the mixture of the three elements formed a compound with molecules that contain two hydrogen atoms, one sulfur atom, and four oxygen atoms, which substance is consumed first?

(d) How many atoms of each remaining element would remain unreacted in the change described in (c)?

Which of the postulates of Dalton's atomic theory explains why we can calculate a theoretical yield for a chemical reaction?

A sample of 0.53 g of carbon dioxide was obtained by heating 1.31 g of calcium carbonate. What is the percent yield for this reaction?

${\text{CaCO}}_3(s)⟶\text{CaO}(s)+{\text{CO}}_2(s)$

Citric acid, C₆H₈O₇, a component of jams, jellies, and fruity soft drinks, is prepared industrially via fermentation of sucrose by the mold Aspergillus niger. The equation representing this reaction is
${\text{C}}_{12}{\text{H}}_{22}{\text{O}}_{11}+{\text{H}}_2\text{O}+3{\text{O}}_2⟶2{\text{C}}_6{\text{H}}_8{\text{O}}_7+4{\text{H}}_2\text{O}$

What mass of citric acid is produced from exactly 1 metric ton (1.000 $\times$ 10³ kg) of sucrose if the yield is 92.30%?