CIE Chemistry (US-0439): Specimen Questions with Answers 123 - 125 of 240

Question number: 123

Short Answer Question▾

Write in Short

Substances can be classified as:

Elements can be divided into:

  1. Define each of the following terms:

    element

Explanation

each of more than one hundred substances that cannot be chemically interconverted or broken down into simpler substances and are primary constituents of matter. Each element is distinguished by its atomic number, i. e. the number of protons in the nuclei of its atoms.

Question number: 124

MCQ▾

Question

Avogadro Number (NA) is the number of atoms or molecules present in ________ mole (s) of a substance.

Choices

Choice (4) Response

a.

3

b.

4

c.

2

d.

1

Answer

d.

Explanation

Avogadro number is the number of atoms or molecules present in one mole of a substance.

It is a constant number having the value.

Let us consider few examples.

Number of atoms present in or 1 mole of

Number of molecules present inor 1 mole of oxygen is

Question number: 125

MCQ▾

Question

Which substance is not involved in the extraction of iron from hematite?

Choices

Choice (4) Response

a.

Carbon

b.

Carbon monoxide

c.

Calcium carbonate

d.

Nitrogen

Answer

d.

Explanation

Correct option is D i. e. nitrogen because from the process calcination extraction of iron from hematite can be done using calcium carbonate and from carbon, carbon mono oxide iron extracted from iron ore by reduction with carbon.