CIE Chemistry Paper-1: Specimen Questions 17 - 18 of 99

Question number: 17

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) Response
a.

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

b.

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

c.

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

d.

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

Answer

a.

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.

Question number: 18

MCQ▾

Question

Compound X is heated with carbon using the apparatus shown.

Brown solid is formed in the reaction tube and the limewater

Brown solid is formed in the reaction tube and the limewater

Finding the compound in this reaction process

A brown solid is seen in test tube and the limewater turns cloudy. What is X?

Choices

Choice (4) Response
a.

sodium oxide

b.

copper (II) oxide

c.

magnesium oxide

d.

calcium oxide

Answer

b.

Explanation

Compound X is Copper (II) oxide.

When Copper (II) oxide is heated with carbon following reaction take place:

2CuO + C - > 2Cu + Co2

When the CO2 reaches in the beaker following reaction takes place:

CO2 + Ca (OH) 2 - > CaCO3 + H2O

When carbon di oxide comes in contact with lime water it produces calcium carbonate and causes the white precipitation in the solution.

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