Name the sodium compound which is used for softening hard water.
$ Mg(OH)_2 $
$ Ca{(OH)} _{3} $
$Al_{2} O _{3} $
$Na _{2} CO _{3} \cdot 10 H _{2} O$
Why does dry $HCl$ gas not change the colour of the dry litmus paper ?
A milkman adds a very small amount of baking soda to fresh milk.
$(a)$ Why does he shift the $pH$ of the fresh milk from $6$ to slightly alkaline ?
$(b)$ Why does this milk take a long time to set as curd ?
A solution reacts with crushed egg-shells to give a gas that turns lime water milky. The solution contains
Write an equation to show the reaction between Plaster of Paris and water.
Why do $HCl$, $HNO_3$, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character ?