Which of the following is a weak acid?

Derive the equation of the relation between the weak base ionization constant $K_b$ and its conjugate acid ionization constant $K_a$.

Which of the following cannot act as a Bronsted base?

At $25^{\circ} C$,$K_{a}$ of formic acid is $1.8 \times 10^{-4}$. What is the $K_{b}$ of $HCOO^{-}$?

The conjugate acid of $S_2O_8^{2-}$ is

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