Question

Which of the following statements about decomposition reactions is true?

a) Decomposition and combustion reactions are the same thing
b) Decomposition and single-displacement reactions are the same thing
c) Decomposition reactions are essentially the opposite of synthesis reactions
d) Decomposition reactions are essentially the opposite of single-displacement reactions

Answer 1

C

Decomposition is of this form: A becomes B+C ... so after the reaction, the element A DECOMPOSES into two smaller elements, B and C.

Synthesis is the opposite: B+C becomes A AFTER THE REACTION.

Hope that helps :))

Answer 2

Answer: c) Decomposition reactions are essentially the opposite of synthesis reactions

Explanation:

1. Decomposition is a type of chemical reaction in which one reactant gives two or more than two products.

Example: $K_2CO_3\rightarrow K_2O+CO_2$

2. Combustion is a type of chemical reaction in which fuel is reacted with oxygen to form carbon dioxide and water.

Example:  $CH_4+O_2 \rightarrow CO_2+2H_2O$

3. Single replacement reaction is a chemical reaction in which more reactive element displaces the less reactive element from its salt solution.

Example: $Mg+2HCl\rightarrow MgCl_2+H_2$

4. Synthesis reaction is a chemical reaction in which two reactants are combining to form one product.

Example: $K_2O+CO_2\rightarrow K_2CO_3$  

Thus synthesis ad decomposition are opposite chemical changes as decomposition is breaking of one reactant to form multiple products and synthesis is formation of one product from multiple reactants.