QAChemistry › Which of the following are decomposition reactions?
Q

Which of the following are decomposition reactions?

1. CH4 (g) + O2 (g) → CO2 (g) + H2O (l)

2. CaO (s) + CO2 (g) → CaCO3 (s)

3. Mg (s) + O2 (g) → MgO (s)

4. PbCO3 (s) → PbO (s) + CO2 (g)

A

Answer: 2. CaO (s) + CO2 (g) → CaCO3 (s) and

4. PbCO3 (s) → PbO (s) + CO2 (g)

In (2), limestone is decomposed under heating to give rise to quicklime and CO2, while (4), is the thermal decomposition of lead to produce PbO and CO2.

Explanation: In the first reaction, methane (CH4 (g)) undergoes a combustion reaction to produce CO2 and H2O.

The third reaction is a combination reaction.

1 year ago
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