IGCSE Chemistry Paper-1: Specimen Questions with Answers 22 - 23 of 99

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Question 22

Question

MCQ▾

A test-tube has damp iron wool and is inverted in water. After 3 days, the water level inside the test-tube rise. Explain cause of rise.

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Choices

Choice (4)

a.

Iron wool has been reduced.

b.

Iron oxide has been formed.

c.

The temperature of the water has risen.

d.

Oxygen has been formed.

Answer

b.

Explanation

Air is composed of Nitrogen - about 78 % , Oxygen

about 21 % , Argon about 1 % and other gasses. These gasses compose 100 % of the air so they exert 100 % of the pressure. IN the test tube, at the beginning, there was the same pressure inside the test tube as outside. As the steel wool started to rust, the oxygen was taken out of the air, therefore the pressure was reduced. Over time, the pressure was reduced by the percentage of oxygen removed … . about 21 % . As the pressure drops, the

pressure on the outside of the test tube pushes the water level up inside the test tube. The iron in the steel wool became an iron oxide.

Question 23

Question

MCQ▾

CO2 gas reacts with aqueous sodium hydroxide. Which type of reaction occurs?

Choices

Choice (4)

a.

oxidation

b.

decomposition

c.

fermentation

d.

neutralisation

Answer

d.

Explanation

The chemical equation depicting the above reaction is:

CO2 (g) + 2NaOH (aq) ⇾ Na2CO3 (aq) + H2O (l)

Neutralization is a type of chemical reaction in which a strong acid and strong base react with each other to form water and salt. Co2 is considered to be a strong acid in gaseous form and NaOH is a strong base. It can be seen that when both reacts water is produced along with a salt Na2CO3 i.e.. sodium carbonate.

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