IGCSE Chemistry: Specimen Questions with Answers 124 - 126 of 240

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

Answer

b.

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 in or 1 mole of oxygen is

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

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.

Which of the following is Not a good absorber of sound?

Answer

c.

Explanation

• Correct option is C because Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor.
• There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles, or using active antinoise sound generators. And metal cupboard comes under category of sound proofing.