IGCSE Chemistry: Specimen Questions with Answers 32 - 34 of 240

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Question 32

Question

MCQ▾

The number of valence electrons in the 2nd group is ________.

Choices

Choice (4)

a.

4

b.

2

c.

3

d.

1

Answer

b.

Explanation

Valence electrons are the electrons present in the outermost shell of an atom. The number of valence electrons is equal to the group number. Therefore the number of valence electrons of the elements in 2nd group is 2.

It can be observed from the following table that each element in 2nd group have 2 valence electrons.

Element in 2nd Group Have 2 Valence

Question 33

Write in Short

Short Answer▾

What is meant by the term enzyme?

Explanation

Enzymes are macro molecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products.

Question 34

Question

MCQ▾

For proper collection and disposal of domestic sewage, which one of the following practices cannot be followed?

Choices

Choice (4)

a.

Wastes should be segregated before disposal.

b.

Rivers and lakes should be used for washing purposes.

c.

Separate septic tanks should be used by each house.

d.

Wastes should be deposited at designated places.

Answer

b.

Explanation

For proper collection and disposal of domestic sewage, rivers and lakes should not be used for washing purposes as it leads to water pollution.

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