What do you mean by a precipitation reaction? Explain by giving examples.
A reaction in which an insoluble solid (called precipitate) is formed is called a precipitation reaction.
For example :
$\mathop {N{a_2}C{O_{3(aq)}}}\limits_{{\text{Sodium carbonate}}} + \mathop {CaC{l_2}_{(aq)}}\limits_{{\text{Calcium chloride}}} \to \mathop {CaC{O_3}_{\left( s \right)}}\limits_{{\text{Calcium}}\,{\text{carbonate}}} + \mathop {2NaC{l_{(aq)}}}\limits_{{\text{Sodium}}\,{\text{chloride}}\,\,} $
In this reaction, calcium carbonate is obtained as a precipitate. Hence, it is a precipitation reaction.
Another example of precipitation reaction is :
$\mathop {N{a_2}S{O_{4(aq)}}}\limits_{{\text{Sodium sulphate}}} \, + \mathop {\,BaC{l_2}_{(aq)}\,}\limits_{{\text{Barium chloride}}} \to \,\mathop {BaS{O_{4(s)}}}\limits_{{\text{Barium sulphate}}} \, + \,\mathop {2NaC{l_{(aq)}}\,}\limits_{{\text{Sodium chloride}}} $
In this reaction, barium sulphate is obtained as a precipitate.
What is the difference between displacement and double displacement reactions ? Write equations for these reactions.
Why do we apply paint on iron articles ?
Oil and fat containing food items are flushed with nitrogen. Why ?
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.
Explain the ''Rancidity'' terms with one example.