Write the conjugate acids for the following Bronsted bases: $NH_{2}^{-}$,$NH_{3}$ and $HCOO^{-}$.

Which of the following pairs cannot exist together in a solution?

State the Lewis acid-base principle.

When $KHSO_4$ is added into a concentrated solution of $H_2SO_4$,the acidity of the solution

In the following acid-base reactions,in which case can the backward reaction be favoured?

Consider the following reaction involving two acids shown below: formic acid and $HF$.
$K^+F^- + HCOOH \rightleftharpoons HCOO^-K^+ + HF$
Given: $pK_a$ of $HCOOH = 3.8$ and $pK_a$ of $HF = 3.2$.
Which of the following statements about this reaction are true?
$(A)$ Formic acid is the strongest Bronsted acid in the reaction
$(B)$ $HF$ is the strongest Bronsted acid in the reaction
$(C)$ $KF$ is the strongest Bronsted base in the reaction
$(D)$ $KO_2CH$ is the strongest Bronsted base in the reaction
$(E)$ The equilibrium favours the reactants
$(F)$ The equilibrium favours the products
$(G)$ Formic acid has a weaker conjugate base
$(H)$ $HF$ has a weaker conjugate base