Question

Which of the following are decomposition reactions?

1. CH4 (g) + O2 (g) --> CO2 (g) + H2O (l)
2. CaO (s) + CO2 (g) --> CaCO(s)
3. Mg (s) + O2 (g) --> MgO (s)
4. PbCO3 (s) --> PbO (s) + CO2 (g)
A. 1, 2, and 3
B. 1, 2, 3, and 4
C. 2 and 3
D. 4 only
E. 2, 3, and 4

Answer 1

The decomposition reactions in the given options are options 1, 3, and 4.

Step-by-step explanation:

The decomposition reactions in the given options are:

• CH4 (g) + O2 (g) → CO2 (g) + H2O (l) - Methane gas reacts with oxygen gas to form carbon dioxide gas and water. This is a decomposition reaction.
• CaO (s) + CO2 (g) → CaCO(s) - Calcium oxide reacts with carbon dioxide gas to form calcium carbonate. This is not a decomposition reaction.
• Mg (s) + O2 (g) → MgO (s) - Magnesium metal reacts with oxygen gas to form magnesium oxide. This is a decomposition reaction.
• PbCO3 (s) → PbO (s) + CO2 (g) - Lead carbonate decomposes to lead oxide and carbon dioxide. This is a decomposition reaction.

Therefore, the decomposition reactions are options 1, 3, and 4. The correct answer is (A) 1, 2, and 3.