IGCSE Chemistry Paper-1: Specimen Questions with Answers 15 - 17 of 99

What is the relative molecular mass, Mr, of HNO₃?

Answer

Explanation

Relative molecular mass is the sum of all the relative atomic masses of the atoms in a molecule.

H= 1, N= 14, O= 16

Therefore

The diagram shows how to obtain pure water from seawater. Where do water molecules lose energy?

Explanation

Here, Sea water contains .

• So, to obtain pure water () , there is a process called desalination is used to convert salt water into pure water.

Desalination Process:

• In this process, sea water is heated by any Bunsen flame as shown in upper figure to convert sea water into gas state.
• Then this gas is condensed to make it liquid which is called distillation process which gives pure water.

Chemical Formula:

Element X forms an acidic, covalent oxide.

Which row shows how many electrons there could be in the outer shell of an atom of X?

Answer

Explanation

They must be 4,5,6 or 7. For example element having 7 electrons on its outer shell such as Cl forms acidic oxide Cl207. Again element with 4 electrons on is outer shell like nitrogen forms NO2 an acidic oxide. Therefore it can have 6 or 7 electrons.