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WAEC Chemistry 2015 Paper

Question : 20

Total: 50

\rightarrow

[Molar Volume of gas = 22.4dm3

Solution:

Concept:

The volume of a gas at s.t.p. is found using the mole ratio from the balanced equation and the molar volume.

Explanation:

From the balanced equation,

\mathrm{C_2H_4(g) + 3O_2(g) \rightarrow 2CO_2(g) + 2H_2O(g)}

1 mole of

\mathrm{C_2H_4}

produces 2 moles of

\mathrm{CO_2}

Therefore, 0.05 moles of

\mathrm{C_2H_4}

produce

0.05 \times 2 = 0.10

moles of

\mathrm{CO_2}

At s.t.p., 1 mole of any gas occupies

22.4\,\mathrm{dm^3}

So, volume of

\mathrm{CO_2}

produced =

0.10 \times 22.4 = 2.24\,\mathrm{dm^3}

Answer:

The volume of

\mathrm{CO_2}

produced is

2.24\,\mathrm{dm^3}

Correct option: B.

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