HKDSE-onward Chemistry Question Review

學術區
41

Question:

Outline how town gas can be produced.

42

Solution:

The neccessary conditions are:

  1. 10 atm
  2. Hot catalyst Ni in 700^\circ\mathrm{C}

Pass gaseous hydrocarbon to a stream of steam, then CO and H_2 will be produced.

43

Question:

Suggest any TWO common poisons in Haber Process.

44

Solution:

  1. oxygen or oxides
  2. sulphur or sulphates
45

Solution:

Brown ring test is used to detect nitrate(V) ions in an aqueous solution.

(a) Suggest the reagents required.
(b) Name the brown ring.

46

Solution

(a) Freshly prepared FeSO_4 (aq) + H_2SO_4(l)
(b) Pentaaquanitrosyliron(II) ion [Fe(H_2O)_5(NO)]^{2+}

47

Question:

With 600 atm pressure, the yield of NH_3 in Haber Process is so high but we choose 250 atm instead. Why?

48

Solution:

It is so costy to maintain a high pressure system. The power dissipated in the compressor will be prohibitively high if 600 atm pressure or above is adopted.

49

Question:

What will happen when we heat Ammonium Nitrate(V) powders?

50

Solution:

The following items will be released:

H_2O(g) + N_2(g) + O_2(g) + heat

i.e. explosion will occur.

51

Question:

NH_3 is a strong reducing agent. Attest it with an example.

52

Solution:

NH_3(g) \to N_2(g) when CuO(s) \to Cu(s)

53

Question:

With catalyst, NH_3 can be further oxidized to NO during combustion. Name the catalyst.

54

Solution:

red-hot Platinum

55

Question:

Which one solid base has more surface area?

  1. Ca(OH)_2 or
  2. NaOH
56

Solution:

1., because it is a powder, not crystal.

57

Question:

What dehydrating agent should be used to dry NH_3?

58

Solution:

CaO (s)

59

Question:

What reagent should be used to detect the existence of NH_3 (g)?

60

Solution:

Wet red litmus paper.