Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy.
Decomposition reaction : $AB +$ Energy $\longrightarrow A + B$
$2{{H}_{2}}{{O}_{(l)}}\xrightarrow{\text{ Electroly}sis}2{{H}_{2(g)}}+{{O}_{2(g)}}$
Combination reaction : $A+B \longrightarrow A B+$ Energy
$2{{H}_{2(g)}}+{{O}_{2(g)}}\to 2{{H}_{2}}{{O}_{(l)}}\,+$ Energy
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
What happens when dilute hydrochloric acid is added to iron fillings ? Tick the correct answer.
Which of the statements about the reaction below are incorrect ?
$2 PbO _{( s )}+ C _{( s )} \longrightarrow 2 Pb _{( s )}+ CO _{2( g )}$
$(a)$ Lead is getting reduced.
$(b)$ Carbon dioxide is getting oxidised.
$(c)$ Carbon is getting oxidised.
$(d)$ Lead oxide is getting reduced.
Translate the following statements into chemical equations and then balance them.
$(a)$ Hydrogen gas combines with nitrogen to form ammonia.
$(b)$ Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
$(c)$ Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
$(d)$ Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.