IGCSE Chemistry: Specimen Questions with Answers 204 - 206 of 240

Question number: 204

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Short Answer Question▾

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The alkanes are a homologous series of hydrocarbons.

  1. What is meant by the term homologous series?

    ……………………………………………………………………………………………………………………

    ……………………………………………………………………………………………………………… (2)

Explanation

In organic chemistry, a homologous series is a series of compounds with the same general formula, usually varying by a single parameter. This can be the length of a carbon chain, for example in the straight-chained alkanes (paraffins), or it could be the number of monomers in a homopolymer such as amylose. As shown in the diagram.

Iamge of Methane CH4

Iamge of Methane CH4

Iamge of Methane CH4

Image of Ethane C2H6

Image of Ethane C2H6

Image of Ethane C2H6

Image of Propane C3H8

Image of Propane C3H8

Image of Propane C3H8

Image of Butane C4H10

Image of Butane C4H10

Image of Butane C4H10

Image of Pentane C5H12

Image of Pentane C5H12

Image of Pentane C5H12

Question number: 205

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Short Answer Question▾

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Suggest why a solution of malonic acid, concentration 0.2 mol/dm3, has a higher pH than one of sulfuric acid of the same concentration.

[1 Marks]

Explanation

Because the sulfuric acid have low melting point and malonic has high melting point than malonic acid.

Question number: 206

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MCQ▾

Question

Which of the statements about ethanol are correct?

1 Ethanol can be formed by an addition reaction.

2 Ethanol can be formed by fermentation.

3 When ethanol burns in air, it forms carbon dioxide and water.

Choices

Choice (4) Response

a.

b.

c.

d.

Answer

a.

Explanation

Correct option is A means all because Ethanol can be made by reacting ethene (from cracking crude oil fractions) with steam. The combustion of ethanol is an exothermic reaction so it forms , and heat. Ethanol can also be formed by fermentation of glucose