Suggested Answers on Note (Chapter 21) P.2

 

Preparation of sulphur dioxide

 

1.        Heating copper with concentrated sulphuric acid

        Cu(s) + 2H₂SO₄(l) ¾® CuSO₄(aq) + SO₂(g) + 2H₂O(l)

       

2.        Warming a sulphite with a dilute acid

                Na₂SO₃(aq)/(s) + 2HCl(aq) ¾® 2NaCl(aq) + SO₂(g) + H₂O(l)

 

        3.        Burning sulphur in air

S(s) + O₂(g) ¾® SO₂(g)

 

 

Suggested Answers on Note (Chapter 21) P.5

 

Bleaching action of sulphur dioxide and sulphite ion

        SO₂(g) + H₂O(l) D H₂SO₃(aq)                     sulphurous acid

        H₂SO₃(aq) ¾® SO₃^2-(aq) + 2H⁺(aq)        source of sulphite ions

       

 

Suggested Answers on Note (Chapter 21) P.7

 

Reducing properties

        SO₂(g)/(aq) + 2H₂O ¾® SO₄^2-(aq) + 4H⁺(aq) + 2e^-

        SO₃^2-(aq) + H₂O ¾® SO₄^2-(aq) + 2H⁺(aq) + 2e^-

 

Reaction of sulphur dioxide or sulphite ion with	Colour change	Equations
Bromine water	Brown ® colourless	Br2 + 2e- ® 2Br-
Acidified potassium dichromate solution	Orange ® green	Cr2O72- + 14H+ + 6e- ® 2Cr3+ + 7H2O
Acidified potassium permanganate solution	Purple ® colourless	MnO4- + 8H+ + 5e- ® Mn2+ + 4H2O
Iron(III) sulphate solution	Yellow ® green	Fe3+ + e- ® Fe2+

 

 

Suggested Answers on Note (Chapter 21) P.8

 

Test for sulphur dioxide

        SO₂(g) + 2H₂O(l) ¾® SO₄^2-(aq) + 4H⁺(aq) + 2e^-

        Cr₂O₇^2-(aq) + 14H⁺(aq) + 6e^- ¾® 2Cr³⁺(aq) + 7H₂O(l)

3SO₂(g) + Cr₂O₇^2-(aq) + 2H⁺(aq) ¾® 3SO₄^2-(aq) + 2Cr³⁺(aq) + H₂O(l)

         

 

Suggested Answers on Note (Chapter 21) P.10 - 12

 

1.	C	6.	B	11.	D	16.	A
2.	D	7.	C	12.	C	17.	B
3.	A	8.	C	13.	B
4.	A	9.	D	14.	B
5.	B	10.	B	15.	A

 

 

Suggested Answers on Note (Chapter 21) P.13 - 14

 

1.	B	6.	D
2.	B
3.	D
4.	A
5.	C

 

 

Suggested Answers on Note (Chapter 21) P.17 - 18

 

1.	B	6.	B	11.	C
2.	C	7.	B	12.	C
3.	D	8.	C	13.	A
4.	B	9.	D	14.	A
5.	B	10.	B

 

 

Suggested Answers on Note (Chapter 21) P.19

 

1.	C
2.	A
3.	A
4.	A

 

 

Suggested Answers on Note (Chapter 21) P.25 - 32

 

1.	B	6.	D	11.	C	16.	D	21.	D
2.	C	7.	A	12.	C	17.	B	22.	B
3.	A	8.	D	13.	A	18.	C	23.	A
4.	B	9.	C	14.	C	19.	C	24.	C
5.	B	10.	A	15.	D	20.	B	25.	A

 

26.	D	31.	B	36.	B	41.	D	46.	A
27.	C	32.	C	37.	D	42.	B	47.	A
28.	B	33.	D	38.	C	43.	D	48.	C
29.	D	34.	C	39.	C	44.	D	49.	C
30.	D	35.	A	40.	A	45.	D	50.	B

 

51.	B	56.	B
52.	D	57.	C
53.	B	58.	D
54.	D
55.	C