SS2: CHEMISTRY – 3RD TERM Sulphur and its Compounds | Week 7 Theory Questions – Sulphur and its Compounds

Lesson 7, Topic 13

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Theory Questions – Sulphur and its Compounds

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Theory Questions & Answers – Sulphur and its Compounds

Theory Questions & Answers – Sulphur and its Compounds:

1. (a). Give two chemical properties of sulphur

(b). Define allotropy and mention the allotropes of sulphur

2. (a). State three properties of hydrogen sulphide

(b). briefly describe rhombic and monoclinic sulphur

3. (a). Describe the contact process

(b). State three physical and three chemical properties of tetraoxosulphate(VI) acid.

(c). Give the laboratory preparation of sulphur (IV) oxide gas.

4. (a). Give two uses each of:

SO₂ gas
H₂SO₄
H₂S

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Theory Questions & Answers

1. (a). Give two chemical properties of sulphur

Answer:

Sulphur combines with coke in an electric furnace to form carbon(IV) sulphide

S_(g) + C_(s) → CS_2(l)

Sulphur combines slowly with hydrogen at high temperature to form hydrogen sulphide.

S_(s) + H_2(g) → H₂S_(g)

(b). Define allotropy and mention the allotropes of sulphur

Answer:

Allotropy is the property of some chemical elements in two or more different forms, in the same physical state.

The allotropes of sulphur

Answer:

Rhombic sulphur
Monoclinic sulphur
Amorphous sulphur

2. (a). State three properties of hydrogen sulphide

Answer:

i. Hydrogen sulphide is a colourless gas with a very offensive smell like that of a rotten egg.

ii. It is sparingly soluble in water at ordinary temperatures but insoluble in boiling water.

iii. It is a poison gas

iv. It has a density of 1.18 g/cm³

(b). briefly describe rhombic and monoclinic sulphur

Answer:

Rhombic sulphur is the form of sulphur at a temperature below 96ºC. They are bright and octahedral. They consist of S₈ ring of atoms. It can be obtained when sulphur crystallizes in its solution with CS₂.

Monoclinic sulphur is the form of sulphur stable at temperatures between 96ºC and 119ºC. It is less dense than rhombic sulphur. It melts at 120ºC.

3. (a). Describe the contact process

Answer: Contact process is the process by which H₂SO₄ is manufactured, industrially.

S_(s) + O_2(g) → SO_4(g)

2SO_4(g) + O_2(g) \( \overset{V_2O_5}{\rightarrow}\) 2SO_3(g)

SO_3(g) + H₂SO_4(aq) → H₂S₂O_7(aq). [oleum]

H₂S₂O_7(aq) + H2O_(l) → 2H₂SO_4(aq)

(b). State three physical and three chemical properties of tetraoxosulphate(VI) acid.

Answer:

Physical Properties

i. It has a density of 1.84g/cm3

ii. It is a hygroscopic substance

iii. It has a boiling point of 338ºC

Chemical Properties

i. It is a strong dibasic acid

H₂SO_4(aq) → 2H⁺_(aq) + SO₄^2-_(aq)

ii. It reacts with bases to form salt and H₂O

iii. It is a very good oxidizing agent

(c). Give the laboratory preparation of sulphur(IV) oxide gas.

Answer: In the laboratory, sulphur(IV) dioxide is prepared by the reaction of potassium or sodium trioxosulphate(IV) with tetraoxosulphate(VI) acid or hydrochloric acid. For example, a reaction between the dilute tetraoxosulphate(VI) acid with sodium trioxosulphate(IV) produces SO₂.

Na₂SO₃ + H₂SO₄ → Na₂SO₄ + H₂O + SO₂

4. (a). Give two uses each of

(i) SO₂ gas

Answer:

Production of tetraoxosulphate(VI) acid.
Used as germicide

(ii) H₂SO₄

Answer:

Used in the purification of crude oil
Used as an electrolyte in lead accumulators/battery

(iii) H₂S

Answer:

Analysis of Ores
Analysis of metals.