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

Question number: 15

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MCQ▾

Question

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

Choices

Choice (4)

a.

63

b.

31

c.

5

d.

32

Answer

a.

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

Question number: 16

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Essay Question▾

Describe in Detail

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

Process of getting pure water

Process of Getting Pure Water

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 figure above 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:

Question number: 17

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MCQ▾

Question

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?

Choices

Choice (4)

a.

1 = N 2 = Y 6 = N 7 = Y

b.

1 = N 2 = N 6 = Y 7 = Y

c.

1 = Y 2 = Y 3 = N 6 = N 7 = N

d.

1 = Y 2 = N 6 = Y 7 = N

Answer

b.

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.

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