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Chem mc

2009-03-20 3:26 am

1: Which of the following substances are used to produce nitric acid in industry?
(1) air (2) water
(3) nitrogen (4) ammonia
A. (1),(2)&(3)only B. (1),(2)&(4)only
C. (1),(3)&(4)only D. (2),(3)&(4)only

2: Which of the following statements concerning the reaction of aqueous ammonia with hydrochloric acid is correct?
A. The reaction is exothermic
B. A white precipitate is formed
C. Ammonium chloride and chlorine are produced
D. The product ammonium chloride is a covalent compound

3: Which of the following substances is/are the main products(s) when a mixture of ammonia and oxygen is passed over red-hot platinum?
(1) nitrogen
(2) nitrogen monoxide
(3) nitric acid
A. (1)only B. (2)only
C. (1)&(3)only D. (2)&(3)only

4: Which of the following experiments would produce sulphur dioxide?
(1) heating iron pyrites in air
(2) heating a mixture of iron and dilute sulphuric acid
(3) heating a mixture of copper and concentrated sulphuric acid
A. (1)&(2)only B. (1)&(3)only
C. (2)&(3)only D. (1),(2)&(3)

5: Which of the following statements concerning household bleach is correct?
A. the active ingredient of household bleach is sodium hydroxide
B. household bleach is produced by dissolving chlorine in water
C. household bleach can be used as a drain opener
D. the raw material for manufacturing household bleach is sodium chloride

6: Which of the following substances can react with magnesium to give a colourless gas which burns with a 'pop' sound?
(1) grape fruit juice
(2) citric acid crystals
(3) household bleach
A. (1)only B. (2)only
C. (1)&(3)only D. (2)&(3)only

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回答 (1)

老爺子

2009-03-20 10:27 am

✔ 最佳答案

1:
The answer is B.

To prepare nitric acid, ammonia firstly reacts with oxygen in air in the presence of platinum catalyst.
4NH3(aq) + 5O2(g) → 4NO(g) + 6H2O(g)

The nitrogen monoxide produced is then converted to nitrogen dioxide when reacting with oxygen in air at room temperature.
2NO(g) + O2 → 2NO2(g)

The nitrogen dioxide then reacts with water in the presence of oxygen in air to give nitric acid.
4NO2(g) + 2H2O(aq) + O2(g) → 4HNO3(aq)

2:
The answer is A.

The equation of the reaction is:
NH3(aq) + HCl(aq) → NH4+(aq) + Cl-(aq) ..ΔH = -ve

A is correct, because the reaction is exothermic.
B is incorrect, because the NH4Cl formed is soluble in water.
C is incorrect, because the no chlorine is formed.
D is incorrect, because ammonium chloride is an ionic compound which contains NH4+ and Cl- ions.

3:
The answer is B.

The equation of the reaction is:
4NH3(aq) + 5O2(g) → 4NO(g) + 6H2O(g)

4:
The answer is B.

Reactions (1) and (3) give sulphur dioxide, but reaction (2) does not.
(1): 4FeS2 + 11O2 → 2Fe2O3 + 8SO2
(2): Fe + H2SO4 → FeSO4 + H2
(3): Cu(s) + 2H2SO4 → CuSO4 + 2H2O + SO2

5:
The answer is D.

A is incorrect.
The active ingredient is sodium hypochlorite.

B is incorrect.
It is produced by dissolving chlorine in cold sodium hydroxide solution.

C is incorrect.
Sodium hydroxide can, but not household bleach.

D is correct.
Sodium chloride is firstly electrolyzed to give chlorine and sodium hydroxide. Chlorine and sodium hydroxide react to give household bleach.

6:
The answer is A.

Magnesium reacts with dilute acids to give hydrogen gas, which burns with a 'pop' sound.
Among them, only (1) is a dilute acid. (2) does not have acid properties because of the absence of water. (3) is an alkaline solution.
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