(a) If in $\mathrm{YCl},\mathrm{Y}$ is sodium, the $\mathrm{pH}$ of the salt solution would be alkaline or basic. This is because the chloride ion $\left({\mathrm{Cl}}^{-}\right)$ is the conjugate base of the strong acid hydrochloric acid $\left(\mathrm{HCl}\right)$ and does not affect the $\mathrm{pH}$ significantly, while the sodium ion $\left({\mathrm{Na}}^{+}\right)$is the conjugate acid of a weak base $\left(\mathrm{NaOH}\right)$ and can act as a source of hydroxide ions $\left({\mathrm{OH}}^{-}\right)$in solution, increasing the $\mathrm{pH}$.
(b) If in salt ${\mathrm{NH}}_4\mathrm{X},\mathrm{X}$ is a nitrate, its solution will give a green colour with a universal indicator. This is because ammonium ion $\left({\mathrm{NH}}_4^{+}\right)$is a weak acid that can partially dissociate to form hydrogen ions $\left({\mathrm{H}}^{+}\right)$in the solution, making the solution acidic. Nitrate ion $\left({\mathrm{NO}}_3^{-}\right)$is a neutral ion and does not affect the $\mathrm{pH}$. The green colour of the solution indicates a $\mathrm{pH}$ between 7 and 6.
(c) If ${\mathrm{ZCO}}_3$ is added to the blue litmus solution and $\mathrm{Z}$ is potassium, the blue litmus solution will turn pink or red. This is because the carbonate ion $\left({\mathrm{CO}}_3^{2-}\right)$ is a strong base that can accept hydrogen ions $\left({\mathrm{H}}^{+}\right)$from water, forming bicarbonate ion $\left({\mathrm{HCO}}_3^{-}\right)$and hydroxide ion $\left({\mathrm{OH}}^{-}\right)$, and increasing the $\mathrm{pH}$. The blue litmus solution, which is a $\mathrm{pH}$ indicator that turns red in acidic conditions, will be affected by the increased $\mathrm{pH}$ and turn pink or red.