(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 $(\mathrm{Cl}^{-})$ is the conjugate base of the strong acid hydrochloric acid $(\mathrm{HCl})$ and does not affect the $\mathrm{pH}$ significantly, while the sodium ion $(\mathrm{Na}^{+})$is the conjugate acid of a weak base $(\mathrm{NaOH})$ and can act as a source of hydroxide ions $(\mathrm{OH}^{-})$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 $(\mathrm{NH}_4^{+})$is a weak acid that can partially dissociate to form hydrogen ions $(\mathrm{H}^{+})$in the solution, making the solution acidic. Nitrate ion $(\mathrm{NO}_3^{-})$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 $(\mathrm{CO}_3^{2-})$ is a strong base that can accept hydrogen ions $(\mathrm{H}^{+})$from water, forming bicarbonate ion $(\mathrm{HCO}_3^{-})$and hydroxide ion $(\mathrm{OH}^{-})$, 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.