Which of the following are decomposition reactions?
A. 2LiOH (s) + CO² (g) --> Li²CO³ (s) + H²O (I)
B. K²CO³ (s) --> K²O (s) + CO² (g)
C. 2SO³ (g) --> 2SO² (g) + O² (g)
D. 2Na (s) + Cl² (g) --> 2NaCl (s)

The 2 decomposition reactions are:

B. (s) --> (s) + (g)

C. (g) --> (g) + (g)

Explanation:

Step 1:

A decomposition reaction is one in which a single compound breaks down into two or more products.

Step 2:

Let us examine each reaction if it satisfies the above rule.

A. 2 LiOH +   ---> +

In this reaction we have 2 reactants giving 2 products. Hence this is not a decomposition reaction.

B. ---> +

In this reaction a single reactant potassium carbonate gives rise to 2 products Potassium Oxide and carbon-di-oxide. Hence this is a decomposition reaction

C. ---> +

In this reaction a single reactant sulfur tri-oxide gives rise to 2 products sulfur di-oxide and oxygen. Hence this is a decomposition reaction.

D. + --->

In this reaction 2 reactants sodium and chlorine gives rise to a single product sodium chloride. Hence this is not a decomposition reaction.

Step 3:

The 2 decomposition reactions are:

B. (s) ---> (s) + (g)

C. ---> +

third one with arrows on top of each other going the same direction