Chemistry Paper 2, 2019

Question 4

1. Name the reagents used in the laboratory preparation of hydrogen chloride gas.
2. Write an equation for the laboratory preparation of hydrogen chloride gas..
3. Describe the laboratory test for HCl_(g)..
1. List three physical properties of metals..
2. Write an equation to illustrate the property of tetraoxosulphate (VI) acid as:
  1. an oxidizing agent..
  2. a dehyadrating agent.
[6 marks]
1. Name the product formed when heated coke is treated with steam.
2. State the components of the product named in 4(c)(i).
3. Name two types of coal
1. Name a metal whose trioxonitrate (V) salt decomposes on heating to give oxygen gas.
2. Write the chemical formula of a binary compound of oxygen that is:
  1. acidic;
  2. amphoteric.
  3. Write an equation to show the amphoteric nature of the compound stated in 4(d)(ii)(II).

State two uses of calcium trioxocarbonate (IV).

[6 marks]

Observation

Majority of the candidates responded to this question, and their performance was above average.

In part (a), majority of the candidates were able to name the reagents used in the laboratory preparation of hydrogen gas. However, they could not correctly write an equation for the laboratory preparation of hydrogen chloride gas.

In part (b), majority of the candidates were familiar with the physical properties of metals. However, they could not write an equation each to illustrate the property of HK₂SO₄ as an oxidizing agent and dehydrating agent.

In part (c), majority of the candidates were able to name the products formed when heated coke is treated with steam. Also, they were able to name types of coal.

In part (d), majority of the candidates were familiar with types of oxides, but could no write an equation to show the amphoteric nature of the compound stated in 4(d) (ii) (II).

In part (e), majority of the candidates were able to state the uses of trioxocarbonate (IV).

The expected answers include:

2. H₂SO,_4(aq)+ NaCl_(s) → NaHSO4_(aq) + HCl_(g)
  
  OR H₂SO₄+ 2NaCl Na₂SO₄ + 2HCl_(g)
3. A glass rod dipped into conc. NH₃ is brought into contact with the test gas.
  
  Dense white fumes are formed to show that the test gas is HCl.
  
  OR Add drops of AgNO_3(ag) or Pb(NO₃)_2(ag) into the jar, white precipitate
  
  shows gas is hydrogen chloride.
1. good electrical conductors
2. 1. Cu(_(s) + 2H₂SO₄(aq) → CuSO₄(aq) + 2H₂O(l) + SO₂(g)
  2. C1₁₂ H₂₂ O_11(s) + H₂SO₄ → 12C(_11(s) + 11H₂O(g)
1. Water gas
2. - Carbon (II) oxide / CO
  - Hydrogen / H₂
3. - Anthracite
  - lignite
  - bituminous
2. 2. BeO
3. - ZnO_(s) + 2NaOH_(aq) → Na₂ZnO₍₂₎(_(aq)+ H₂O_(aq)
  - ZnO_(s) + 2HCl_(aq)→ ZnCl₂(_(aq) H₂O_(l)
  - Al2O₃+ 6HCl 2AlCl₃ + 3H₂O
  - Al₂O₃ + 2NaOH + 3H₂O 2NaAl(OH)₄
  - SnO₂ + 2H₂SO₄ →Sn(SO₄)₂+ 2H₂O
  - SnO₂+ 2KOH+2H₂O K₂Sn(OH)₆
- (abrasive) in tooth paste
- paper filler (to brighten and retain ink).
- antacid
- extraction of iron.
- manufacture of cement.
- production of chalk.
- to neutralize acidic soil / liming of soil.
- in adhesives and sealants.
- making glass.
- making CO₂ quicklime / CaO.

Chemistry Paper 2 WASSCE (PRIVATE CANDIDATE), 2019

Question 4

Observation