$A$ solution of sodium bicarbonate in water turns:

The $pH$ of $0.1 \ M$ solution of the following salts increases in the order:

In which of the following mixed aqueous solutions,$pH = pK_{a}$ at equilibrium?
$(1)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ CH_{3}COONa$
$(2)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 50 \ mL$ of $0.1 \ M \ NaOH$
$(3)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ NaOH$
$(4)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ NH_{3}$

Given below are two statements :
Statement $I$ : Aqueous solution of ammonium carbonate is basic.
Statement $II$ : Acidic/basic nature of salt solution of a salt of weak acid and weak base depends on $K_a$ and $K_b$ value of acid and the base forming it.
In the light of the above statements,choose the most appropriate answer from the options given below :

The dissociation constant of acetic acid is $1.6 \times 10^{-5}$ and $\Lambda _{CH_3COOH}^o = 370.6 \times 10^{-4} \, S \, m^2 \, mol^{-1}$. The specific conductance of $0.01 \, M$ acetic acid solution will be approximately:

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