CIE Chemistry (US-0439): Specimen Questions with Answers 141 - 142 of 240

Question number: 141

MCQ▾

Question

Below are some metals in decreasing order of reactivity.

Magnesium

Zinc

Iron copper

Titanium reacts with acid and cannot be extracted from its ore by heating with carbon. Where should titanium be placed in this list?

Choices

Choice (4) Response

a.

Below copper

b.

Between iron and copper

c.

Between magnesium and zinc

d.

Between zinc and iron

Answer

c.

Explanation

Correct option is C i. e. between magnesium and zinc because it reacts with concentrated mineral acids and extraction using magnesium, or less commonly other alkali metals, hydrogen or calcium in the Kroll process.

Question number: 142

MCQ▾

Question

An industry manufactures a medicinal drug comprising of nitric oxide (NO), which is used as an energy booster. NO is produced by a reaction involving oxidation of ammonia.

If 55 liters of ammonia is used, the amount of NO produced is ________.

Choices

Choice (4) Response

a.

55

b.

35

c.

25

d.

45

Answer

a.

Explanation

  • “Gay-Lussac’s Law of Combining Volumes” states that “when gases react, they do so in volumes which bear a simple whole number ratio to one another and to the volume of the gaseous product, provided that all the volumes are measured at the same temperature and pressure”.

  • NO is produced by a reaction involving oxidation of ammonia.

  • The ‘l’ in brackets denotes that water is in liquid state. Other reactants and product have no state mentioned which means that they are in gaseous state. Since change in volume of liquid due to slight change in temperature is negligible, hence its volume is considered to be zero. So liquid is not considered while calculation.

  • Here 4 volumes of NH3 produces 4 volumes of NO.

  • Thus, 1 litre of NH3 produces 1 litre of NO.

  • So 55 litres of NH3 will produce 55 litres of NO.