CHAPTER 19

Neutralization and salts

1.None of them

2.D

3.C

4.D

5.A

6.A

7.D

8.A

9.C

10.B

11.B

12.(a)The tablets contain solid citric acid. When water is added, H+(aq) ions are formed which react with the hydrogencarbonate to give off a gas carbon dioxide.

(b)Should be stored in a cool, dry place. In the presence of moisture, the constituents will react and break down.

(c)Solution of Alka-Seltzer is alkaline. It can neutralize the excess hydrochloric acid (in stomach), which causes stomach pain. Besides, the aspirin itself can relieve pain.

(d)(i)An acid
(ii)Acetylsalicylic acid

13.(a)Mg(s) + 2CH3COOH(aq)(CH3COO)2Mg(aq) + H2(g)
magnesium ethanoate

Mg(s) + 2H+(aq)Mg2+(aq) + H2(g)

(b)Al2O3(s) + 3H2SO4(aq)Al2(SO4)3(aq) + 3H2O(l)
aluminium sulphate

Al2O3(s) + 6H+(aq) 2Al3+(aq) + 3H2O(l)

(c)Ca(OH)2(s) + 2HNO3(aq)Ca(NO3)2(aq) + 2H2O(l)
calcium nitrate

Ca(OH)2(s) + 2H+(aq)Ca2+(aq) + 2H2O(l)

(d)CuCO3(s) + 2HCl(aq)CuCl2(aq) + CO2(g) + H2O(l)
copper(II) chloride

CuCO3(s) + 2H+(aq)Cu2+(aq) + CO2(g) + H2O(l)

(e)Na2SO4(aq) + Pb(NO3)2(aq)PbSO4(s) + 2NaNO3(aq)

lead(II) sulphate sodium nitrate

Pb2+(aq) + SO42(aq)PbSO4(s)

(f)2Na(s) + Cl2(g)2NaCl(s)
sodium chloride

No ionic equation can be written.

14.(a)ZnO(s) + H2SO4(aq)ZnSO4(aq) + H2O(l);

ZnSO4 + 7H2OZnSO47H2O

(b)K2CO3(aq) + H2SO4(aq)K2SO4(aq) + CO2(g) + H2O(l)

(c)AgNO3(aq) + NaBr(aq)AgBr(s) + NaNO3(aq)

(d)BaCO3(s) + 2HCl(aq)BaCl2(aq) + CO2(g) + H2O(l);

BaCl2(aq) + H2SO4(aq)BaSO4(s) + 2HCl(aq)

15.(a)Beaker, heat-resistant mat, Bunsen burner, tripod, wire gauze, spatula, glass rod, evaporating basin, filter funnel, filter paper, filter stand, washbottle

(b)Important points in the method are:

(i) Add excess copper(II) oxide to sulphuric acid.
(ii) Filter to remove excess unreacted copper(II) oxide.
(iii) Boil to concentrate the filtrate (tested with a glass rod).
(iv) Cool the hot concentrated solution to obtain crystals.
(v) Filter, wash and dry the crystals.

16.(a)Fe(s) + H2SO4(aq)FeSO4(aq) + H2(g);

FeSO4 + 7H2OFeSO4 7H2O

(b)To ensure that no acid is left; excess acid will contaminate the salt solution.

(c)Evolution of gas bubbles (H2) stops.

(d)To remove excess iron.

(e)On heating, some iron(II) sulphate will be oxidized by air to produce iron(III) sulphate.

(f)Fe2(SO4)3.

(g)Addition of sodium hydroxide solution to their aqueous solutions to give gelatinous precipitates. Iron(II) hydroxide is dirty green, iron(III) hydroxide is reddish brown.

17.The reaction is: H2SO4(aq) + Ba(OH)2(aq) BaSO4(s) + 2H2O(l)

(a)There is a gradual decrease in ionic concentration and hence conductivity, as Ba2+(aq) and SO42(aq) ions combine to form insoluble BaSO4(s), and H+(aq) and OH(aq) combine to form H2O(l) molecules.

(b)All the acid present is completely neutralized by Ba(OH)2 at B. As all ions are removed from solution, conductivity is zero.

(c)There is an increase in ionic concentration and hence conductivity, due to excess Ba(OH)2(aq), which contains Ba2+(aq) and OH(aq) ions.