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Chapter 4: Problem 87

Balance each of the following oxidation-reduction reactions by using the oxidation states method. a. \(\mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)\) b. \(\mathrm{Mg}(s)+\mathrm{HCl}(a q) \rightarrow \mathrm{Mg}^{2+}(a q)+\mathrm{Cl}^{-}(a q)+\mathrm{H}_{2}(g)\) c. \(\mathrm{Co}^{3+}(a q)+\mathrm{Ni}(s) \rightarrow \mathrm{Co}^{2+}(a q)+\mathrm{Ni}^{2+}(a q)\) d. \(\mathrm{Zn}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{ZnSO}_{4}(a q)+\mathrm{H}_{2}(g)\)

Short Answer

Expert verified
a. \(C_2H_6(g) + O_2(g) \rightarrow 2 CO_2(g) + 7 H_2O(g)\) b. \(Mg(s) + 2 HCl(aq) \rightarrow Mg^{2+}(aq) + 2 Cl^-(aq) + H_2(g)\) c. \(Co^{3+}(aq) + Ni(s) \rightarrow Co^{2+}(aq) + Ni^{2+}(aq)\) d. \(Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(aq) + H_2(g)\)

Step by step solution

01

Identify the oxidation states

Identify the oxidation states of each element in the reactants and products. C2H6: C = -3, H = +1, O = 0 CO2: C = +4, O = -2 H2O: H = +1, O = -2
02

Find the changes in oxidation states

Determine the changes in oxidation states for each element that undergoes a change. C : -3 -> +4 (change of +7) O : 0 -> -2 (change of -2)
03

Balance the changes in oxidation states

Balance the changes in oxidation states by multiplying the number of atoms by the oxidation states changes. C : 2 atoms * (+7) = +14 O : 2 atoms * (-2) = -4 Since C has 14 units increment and O has 4 units decrement, we must multiply the whole H2O by 7 to balance the oxidation states. C2H6(g) + O2(g) -> 2 CO2(g) + 7 H2O(g) b. Mg(s) + HCl(aq) -> Mg2+(aq) + Cl^-(aq) + H2(g)
04

Identify the oxidation states

Identify the oxidation states of each element in the reactants and products. Mg: 0 HCl: H = +1, Cl = -1 Mg2+: +2 Cl^-: -1 H2: 0
05

Find the changes in oxidation states

Determine the changes in oxidation states for each element that undergoes a change. Mg: 0 -> +2 (change of +2) H: +1 -> 0 (change of -1)
06

Balance the changes in oxidation states

Balance the changes in oxidation states by balancing the number of atoms that change oxidation states. In this case, we see that 1 Mg atom changes from Mg to Mg2+ and 2 H atoms from HCl change to H2. So, we just need to multiply HCl by 2 to balance the equation. Mg(s) + 2 HCl(aq) -> Mg2+(aq) + 2 Cl^-(aq) + H2(g) c. Co3+(aq) + Ni(s) -> Co2+(aq) + Ni2+(aq)
07

Identify the oxidation states

Identify the oxidation states of each element in the reactants and products. Co3+: +3 Ni: 0 Co2+: +2 Ni2+: +2
08

Find the changes in oxidation states

Determine the changes in oxidation states for each element that undergoes a change. Co: +3 -> +2 (change of -1) Ni: 0 -> +2 (change of +2)
09

Balance the changes in oxidation states

Balance the changes in oxidation states by balancing the number of atoms that change oxidation states. In this case, since the changes in oxidation states are already balanced, the equation is already balanced: Co3+(aq) + Ni(s) -> Co2+(aq) + Ni2+(aq) d. Zn(s) + H2SO4(aq) -> ZnSO4(aq) + H2(g)
10

Identify the oxidation states

Identify the oxidation states of each element in the reactants and products. Zn: 0 H2SO4: H = +1, S = +6, O = -2 ZnSO4: Zn = +2, S = +6, O = -2 H2: 0
11

Find the changes in oxidation states

Determine the changes in oxidation states for each element that undergoes a change. Zn: 0 -> +2 (change of +2) H: +1 -> 0 (change of -1)
12

Balance the changes in oxidation states

Balance the changes in oxidation states by balancing the number of atoms that change oxidation states. In this case, we see that 1 Zn atom changes from Zn to Zn2+ and 2 H atoms change from H2SO4 to H2. So, the equation is already balanced: Zn(s) + H2SO4(aq) -> ZnSO4(aq) + H2(g)

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Most popular questions from this chapter

You are given a \(1.50-\mathrm{g}\) mixture of sodium nitrate and sodium chloride. You dissolve this mixture into \(100 \mathrm{~mL}\) of water and then add an excess of \(0.500 \mathrm{M}\) silver nitrate solution. You produce a white solid, which you then collect, dry, and measure. The white solid has a mass of \(0.641 \mathrm{~g}\). a. If you had an extremely magnified view of the solution (to the atomic- molecular level), list the species you would see (include charges, if any). b. Write the balanced net ionic equation for the reaction that produces the solid. Include phases and charges. c. Calculate the percent sodium chloride in the original unknown mixture.

A 0.500-L sample of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) solution was analyzed by taking a \(100.0-\mathrm{mL}\) aliquot and adding \(50.0 \mathrm{~mL}\) of \(0.213 M \mathrm{NaOH}\). After the reaction occurred, an excess of \(\mathrm{OH}^{-}\) ions remained in the solution. The excess base required \(13.21 \mathrm{~mL}\) of \(0.103 \mathrm{M} \mathrm{HCl}\) for neutralization. Calculate the molarity of the original sample of \(\mathrm{H}_{2} \mathrm{SO}_{4}\). Sulfuric acid has two acidic hydrogens.

Commercial cold packs and hot packs are available for treating athletic injuries. Both types contain a pouch of water and a dry chemical. When the pack is struck, the pouch of water breaks, dissolving the chemical, and the solution becomes either hot or cold. Many hot packs use magnesium sulfate, and many cold packs use ammonium nitrate. Write reactions to show how these strong electrolytes break apart when they dissolve in water.

A \(1.42-\mathrm{g}\) sample of a pure compound, with formula \(\mathrm{M}_{2} \mathrm{SO}_{4}\), was dissolved in water and treated with an excess of aqueous calcium chloride, resulting in the precipitation of all the sulfate ions as calcium sulfate. The precipitate was collected, dried, and found to weigh \(1.36 \mathrm{~g}\). Determine the atomic mass of \(\mathrm{M}\), and identify \(\mathrm{M}\).

Write the balanced formula equation for the acid-base reactions that occur when the following are mixed. a. potassium hydroxide (aqueous) and nitric acid b. barium hydroxide (aqueous) and hydrochloric acid c. perchloric acid \(\left[\mathrm{HClO}_{4}(a q)\right]\) and solid iron(III) hydroxide d. solid silver hydroxide and hydrobromic acid e. aqueous strontium hydroxide and hydroiodic acid
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