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

Explanation:

in a combination reaction two or more substances are combined to form new substance while in the decomposition reaction one substance decomposes in to two or more substances.

Cu + 2 AgNO3 -> Cu(NO3)2 + 2 Ag

Answer 2

Explanation:

(a) Decomposition and combination reaction:

• The decomposition reaction involves single reactant which decomposes to form two or more products.

        $2 H_{2} O_{2} \rightarrow 2 H_{2} O+O_{2}$

• In the above reaction, the hydrogen peroxide is decomposed into water and hydrogen.
• The combination reaction involves combination of more than one reactants to form a single product.

       $2 M g+O_{2} \rightarrow 2 M g O$

• In the above reaction, the magnesium reacts with oxygen to form magnesium oxide.

(b) Chemical reaction:

       $C u+2 A g N O_{3} \rightarrow 2 A g \downarrow+C u\left(N O_{3}\right)_{2}$

• In the above reaction, copper replaces the silver in the nitrate to form copper nitrate. Copper metal is much reactive than silver metal.