CIE Chemistry Paper-1: Specimen Questions 14 - 16 of 99

Question number: 14

MCQ▾

Question

What is always true for a pure substance?

Choices

Choice (4) Response
a.

It always boils at 100 °Celsius.

b.

It is solid at room temperature

c.

It has a sharp melting point.

d.

It contains only one type of atom

Answer

c.

Explanation

A pure substance is homogeneous, i.e., has uniform composition throughout the whole sample. Pure substances display a sharp melting and boiling point which means that that the material goes from solid to liquid in a very short temperature range. An impure substance would have a melting point with a broader range.

Question number: 15

MCQ▾

Question

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

Choices

Choice (4) Response
a.

63

b.

31

c.

32

d.

5

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 1+14+3×16=1+14+48=63

Question number: 16

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

Showing process of converting sea water into pure water

Explanation

Here, Sea water contains H2O(water)+NaCl(Salt) .

  • So, to obtain pure water ( H2O ), 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:

NaCl(aq)NaCl(s)+H2O(g)

H2O(g)H2O(l)

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