$A$ sample of $Na_2CO_3 \cdot H_2O$ weighing $0.62 \ g$ is added to $100 \ mL$ of $0.1 \ N \ (NH_4)_2SO_4$ solution. What will be the nature of the resulting solution?

At $27^{\circ}C$,$100 \ mL$ of $0.4 \ M$ $HCl$ is mixed with $100 \ mL$ of $0.5 \ M$ $NaOH$ solution. To the resultant solution,$800 \ mL$ of distilled water is added. What is the $pH$ of the final solution?

What is the ratio of the number of $H^{+}$ ions to the number of $H_2O$ molecules in $1 \ L$ of water?

When $NaCl$ is dissolved in water,the sodium ion is

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 species present in solution when $CO_2$ is dissolved in water are