Chile saltpetre is

Equimolar solutions of the following compounds are prepared separately in water. Which will have the lowest $pH$ value?

Among the following,the incorrect statement is

The number of alkali metal$(s)$,from $Li$,$K$,$Cs$,$Rb$ having ionization enthalpy greater than $400 \ kJ \ mol^{-1}$ and forming stable super oxide is $.......$

Given below are two statements:
Statement $I$: The chlorides of $Be$ and $Al$ have $Cl^{-}$-bridged structure. Both are soluble in organic solvents and act as Lewis acids.
Statement $II$: Hydroxides of $Be$ and $Al$ dissolve in excess alkali to give beryllate and aluminate ions.
In the light of the above statements,choose the correct answer from the options given below.

Match the following:

Compound	Uses
$1$. Soda ash	$a$. In purification of sugar
$2$. Calcium oxide	$b$. As an antacid
$3$. Baking soda	$c$. In paper and textile industries
	$d$. To prepare pure fats and oils