Question

(a) Why are decomposition reactions called the opposite of combination reactions? Explain with equations of these reactions.
(b) Express the following facts in the form of a balanced chemical equation:
"When a strip of copper metal is placed in a solution of silver nitrate, metallic silver is precipitated and a solution containing copper nitrate is formed".

Answer 1

(a) In decomposition reaction, a compound breaks down to two or more simple products, whereas in combination reaction, two or more reactants combine to form a single product. Therefore, both the reactions are opposite to each other.

For example, in a combination reaction, simple molecules of hydrogen and oxygen combine to form a water molecule.
2H₂ (g) + O₂ (g) → 2H₂O (l)

While in decomposition reaction, reverse process takes place—​i.e., water decomposes to hydrogen and oxygen.
2H₂O (l) → 2H₂ (g) + O₂ (g)

(b) The balanced chemical equation is given as follows:
Cu (s) + 2AgNO₃ (aq) → Cu(NO₃)₂ (aq) + 2Ag (s)