IGCSE Chemistry Paper-1: Specimen Questions with Answers 37 - 39 of 99

Question number: 37

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Question

The red colour in some pottery glazes may be formed as a result of the reactions shown.

CuO + SnO - > Cu + SnO2

CuCO3 - > CuO + CO2

These equations show that ……1…… is oxidised and ……2…… is reduced. Which substances correctly complete gaps 1 and 2 in the above sentence?

Choices

Choice (4)

a.

1 = CuO 2 = SnO

b.

1 = CuCO3 2 = CuO

c.

1 = CO2 2 = SnO2

d.

1 = SnO 2 = CuO

Answer

d.

Explanation

Oxidation means gain of oxygen and reduction means loss of oxygen.

CuO + SnO - > Cu + SnO2

In the above reaction we can see that CuO turns into Cu (i. e. loss of oxygen). Hence it is a reduction reaction whereas SnO turns to SnO2 (i. e. gain of oxygen) therefore an oxidation reaction.

Question number: 38

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Question

Element X has a nucleon number of 19 and a proton number of 9.

Which group in the Periodic Table does it belong to?

Choices

Choice (4)

a.

VIII

b.

III

c.

I

d.

VII

Answer

d.

Explanation

Given, Proton number/Atomic number of element = 9

Electronic configuration of the element will be 1s² 2s² 2p⁵

Since last sub shell is p group is group is A

Adding 2 + 5 = 7

Therefore group will be 7A

Question number: 39

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Question

What explains combination reaction?

Choices

Choice (4)

a.

Zn (s) +CuSO4 (aq) - > ZnSO4 (aq) + Cu (s)

b.

AgNO3 (aq) + NaCl (aq) - > AgCl (s) + NaNO3 (aq)

c.

C (s) + O2 (g) - > CO2 (g)

d.

All of the above

Answer

c.

Explanation

A combination reaction is a reaction in which two reactants combine to form one product. Oxygen and the halogens are very reactive elements and are likely to undergo combination reactions with other elements. In the above example carbon combines with oxygen to form carbon dioxide.

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