At $25^{\circ} C$,if $[OH^{-}] < 10^{-8} \ M$,then the possible nature of the aqueous solution is$-$

$A$ base is dissolved in water to yield a solution with a hydroxide ion concentration of $0.05 \ mol \ L^{-1}$. The solution is

When a solution of $NaOH$ is left exposed to air for a few hours,what happens?

Which of the following compounds acts as a $Lewis$ base?

For the following two acid-base reactions,which statement is True?
$(I) CH_3CH_2^- + CH_3NH_2$ $(pK_a = 35)$ $\rightleftharpoons CH_3CH_3$ $(pK_a = 50)$ $+ CH_3NH^-$
$(II) F^- + H_2O$ $(pK_a = 15.7)$ $\rightleftharpoons HF$ $(pK_a = 3.2)$ $+ HO^-$

Four species are listed below:
$i. \, HCO_3^-$
$ii. \, H_3O^{+}$
$iii. \, HSO_4^-$
$iv. \, HSO_3F$
Which one of the following is the correct sequence of their acid strength?