IGCSE Chemistry Paper-1: Specimen Questions with Answers 62 - 64 of 99

Question number: 62

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Question

Which of the following statements are true for unsaturated cyclic hydrocarbons?

i) Unsaturated cyclic hydrocarbons are those in which there is a single Carbon to carbon bond.

ii) Unsaturated hydrocarbons are those which do not contain more than six carbon atoms.

iii) Unsaturated hydrocarbons are called as aromatic compounds.

iv) None of these.

Choices

Choice (4) Response

a.

i) and iii)

b.

Only iv)

c.

Only iii)

d.

ii) and i)

Answer

c.

Explanation

The term ‘aromatic’ was assigned before the physical mechanism determining was discovered; the term was coined as such simply because many of the aromatic compounds have a sweet or pleasant odour.

Question number: 63

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Question

What is the nature of calcium phosphate?

Ca3O8P2

Choices

Choice (4) Response

a.

Neutral

b.

Acidic

c.

Basic

d.

All of the above

Answer

c.

Explanation

Description: Calcium phosphate is basic salt, as it is a salt of weak acid (phosphoric acid) and slightly stronger base (calcium hydroxide) (though both are weak). Also when pH of our mouth falls below 5.5 due to eating of sweets etc. , i. e. , mouth is acidic, the dissolution of enamel (calcium phosphate) starts which shows that calcium phosphate is basic in nature.

Question number: 64

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Question

Which gas can be filled to prevent the chips from getting oxidised?

Choices

Choice (4) Response

a.

Carbon di oxide

b.

Oxygen

c.

Hydrogen

d.

Nitrogen

Answer

d.

Explanation

When fats and oils are oxidised, they become rancid and their smell and taste change. Usually substances which prevent oxidation (antioxidants) are added to foods containing fats and oil. Keeping food in air tight containers helps to slow down oxidation. Therefore nitrogen is added to slow down the oxidation process.