Identify the substances that are oxidised and the substances that are reduced in the following reactions.
$(i)$ $4 Na ( s )+ O _{2}( g ) \rightarrow 2 Na _{2} O ( s )$
$(ii)$ $CuO ( s )+ H _{2}( g ) \rightarrow Cu ( s )+ H _{2} O ( l )$
$(i)$ Sodium $(Na)$ is oxidised as it gains oxygen and oxygen gets reduced.
$(ii)$ Copper oxide $(CuO)$ is reduced to copper $(Cu)$ while hydrogen $(H_2)$ gets oxidised to water $(H_2O)$.
A solution of a substance $‘X’$ is used for whitewashing.
$(i)$ Name the substance $‘X’$ and write its formula.
$(ii)$ Write the reaction of the substance $‘X’$ named in $(i)$ above with water.
What does one mean by exothermic and endothermic reactions ? Give examples.
A shiny brown coloured element $‘X’$ on heating in air becomes black in colour. Name the element $‘X’$ and the black coloured compound formed.
$Fe _{2} O _{3}+2 Al \rightarrow Al _{2} O _{3}+2 Fe$
The above reaction is an example of a
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.