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Grade 11 Chemistry Effective Homework 7: Applications of Salt Hydrolysis | Brief Solutions
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1 Evaporate aluminum chloride solution and heat strongly; identify the final solid. Show answer
2 Equal-concentration XCl, YCl and ZCl have pH 4, 5 and 6; compare the corresponding bases. Show answer
3 NaOH and sodium acetate solutions both have pH 9; compare hydroxide concentrations a and b arising from water ionization. Show answer
4 Choose the incorrect statements about acetic acid and acetates. Show answer
5 Select suitable reagents for removing iron(III) from acidic magnesium chloride solution. Show answer
6 Choose the incorrect application involving soda ash, alum, plant ash or a foam extinguisher. Show answer
7 Explain hydrogen and ammonia formation when magnesium is added to ammonium chloride solution. Show answer
8 Interpret the pH curve as sodium sulfite solution is heated and then cooled. Show answer
9 Recover iron(II) chloride tetrahydrate from circuit-board etchant; choose the incorrect operation. Show answer
10 Titrate acetic acid with equal-concentration NaOH; assess M, Q and N on the pOH–pH graph on page 2. Show answer
The given information does not establish a valid option. Q is neutral before complete neutralization, so D is false. At alkaline N, charge balance gives $c(\mathrm{CH_3COO^-})<c(\mathrm{Na^+})$, so B is false. Symmetric pH/pOH values alone do not establish equal water ionization at M and N; C needs additional conditions.
11 Rank the pH of the seven equal-concentration solutions listed in the original question. Show answer
7 > 2 > 1 > 5 > 3 > 4 > 6
12.1 Explain with an ionic equation why aluminum sulfide cannot be prepared in aqueous solution. Show answer
$2\mathrm{Al^{3+}}+3\mathrm{S^{2-}}+6\mathrm{H_2O}\rightarrow2\mathrm{Al(OH)_3}\downarrow+3\mathrm{H_2S}\uparrow$
12.2 Select reagents for removing a small amount of iron(III) chloride from copper(II) chloride. Show answer
12.3 Obtain solid magnesium chloride from its aqueous solution. Show answer
Concentrate in an HCl atmosphere, cool to crystallize and filter; then dehydrate by heating in dry HCl gas.
12.4 Evaporate calcium hypochlorite solution and heat strongly; give the final solid. Show answer
12.5① Use the acid constants to write the reaction of a small amount of carbon dioxide with sodium cyanide solution. Show answer
$\mathrm{CN^-+CO_2+H_2O\rightarrow HCN+HCO_3^-}$
12.5② Select changes that increase acetate concentration while decreasing hydrogen-ion concentration in acetic acid solution. Show answer
12.6 Mix NaOH of pH 12 and sulfuric acid of pH 3 in a 1:9 volume ratio; find the room-temperature pH. Show answer
12.7 Add sulfur dioxide to sodium sulfite solution until neutral; rank the ion concentrations. Show answer
$c(\mathrm{Na^+})>c(\mathrm{HSO_3^-})>c(\mathrm{SO_3^{2-}})>c(\mathrm{H^+})=c(\mathrm{OH^-})$
13.1 Copper scraps containing iron are roasted and treated with excess dilute sulfuric acid; identify the metal ions in solution B. Show answer
$\mathrm{Cu^{2+},Fe^{2+},Fe^{3+}}$
13.2 Select suitable oxidants X in the copper sulfate pentahydrate preparation. Show answer
13.3 Remove iron by pH adjustment; give precipitate D, a suitable reagent and the pH range. Show answer
$\mathrm{Fe(OH)_3}$; $\mathrm{CuO}$ (or $\mathrm{Cu(OH)_2}$); $3.7\leq\mathrm{pH}<4.4$.
13.4 State how to prepare iron(III) chloride solution in the laboratory. Show answer
Dissolve iron(III) chloride in a small amount of concentrated hydrochloric acid, then dilute to the required concentration to suppress hydrolysis.
13.5 Give the two operations before filtration to obtain copper sulfate pentahydrate from solution E. Show answer
Concentrate by evaporation; cool to crystallize.
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