Question

Answer all of the following questions. Each question will have two parts—writing the balanced chemical equation and
answering a question about the reaction. Coefficients in the balanced chemical equation must be in the lowest whole-
number ratio. Do not include formulas for substances that remain unchanged during the reaction. Unless otherwise
noted, assume all the reactions occur in aqueous solution. If a substance is extensively ionized and therefore present as
ions in solution, write its formula as ions

a). Excess sodium hydroxide is added to an aluminum sulfate solution. Which species behaves as a Lewis acid in the
reaction? Explain.

b). Dichlorine heptaoxide is mixed with water. What is the oxidation number of the chlorine in the product.

c). A lead(II) nitrate solution is mixed with ammonium sulfate solution. Which ions, if any, are spectator ions in this reaction?

d). Solid manganese(IV) oxide is added to concentrated hydrochloric acid. What is the oxidation number of the species being oxidized before and after the reaction takes place?

Answer 1

a] Al2(SO4)3 (aq) + 6NaOH (aq) -> 3Na2SO4 (aq) + 2Al(OH)3 (s)

Net ionic equation :

2Al 3+ (aq) + 6OH- (aq) -> 2Al(OH)3 (s)

Lewis acid = Al+3

Lewis acid = A species that accepts electron pair is called Lewis Acid

b] Cl₂O₇ + H₂O → 2HClO₄

Cl oxidation number = +7

c] Molecular equation:
Pb(NO3)2 (aq) + [NH4]2SO4 (aq) -----> PbSO4 (s) + 2NH4NO3 (aq)
Total ionic:
Pb2+ (aq) + 2NO3- (aq) + 2NH4+ (aq) + SO42- (aq) -----> PbSO4 (s) + 2NH4+ (aq) + 2NO3- (aq)
Net ionic:
Pb2+ (aq) + SO4 2- (aq) -----> PbSO4 (s)

NH4+ and NO3- are spectator ions since NH4NO3 is soluble.

d] 4 HCl (aq) + MnO2(s) --> 2H2O (l) + MnCl2 (aq) + Cl2 (g)

Cl- is oxidised

OXidation number before oxidised of Cl is -1

Oxidation number after oxidised is 0