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WAEC Chemistry 2019 Paper

Question : 6

Total: 50

Solution:

Concept:

The reaction between magnesium and hydrochloric acid produces hydrogen gas in a fixed mole ratio.

Explanation:

The balanced equation is:

\mathrm{Mg} + 2\mathrm{HCl} \rightarrow \mathrm{MgCl}_2 + \mathrm{H}_2

From the equation,

24

g of

\mathrm{Mg}

produces

2

g of

\mathrm{H}_2

For

6.5

g of

\mathrm{Mg}

\text{Mass of } \mathrm{H}_2 = 6.5 \times \frac{2}{24}

= \frac{13}{24}

= 0.5416 \text{ g} \approx 0.54 \text{ g}

Answer:

0.54

g of hydrogen gas is liberated.

Correct option: A. 0.54g

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