Question

Alex had two solutions: X and Y. He added a few drops of turmeric water in solution X and observed that the solution X turned yellow in colour. On adding turmeric water to solution Y, he observed that the solution turned red in colour. From the options given below, identify the solutions that match Alex’s observations.

• A. $X:{\mathrm{Na}}_2{\mathrm{CO}}_3;Y:{\mathrm{NH}}_4\mathrm{Cl}$
• B. $X:{\mathrm{NH}}_4\mathrm{Cl};Y:\mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2$
• C. $X:{\mathrm{NH}}_4\mathrm{Cl};Y:{\mathrm{Na}}_2{\mathrm{CO}}_3$
• D. $X:\mathrm{NaCl};Y:K_2{\mathrm{SO}}_4$

Answer 1

The correct option is C $X:{\mathrm{NH}}_4\mathrm{Cl};Y:{\mathrm{Na}}_2{\mathrm{CO}}_3$

Turmeric water is a visual indicator. In the presence of acids, its colour remains yellow, while in the presence of bases, its colour changes to red.
Now, the given salts can be categorised as acidic, basic, and neutral salts based on the acid and base from which the salt has been made.

Salt	Acid	Base	Nature of salt	Colour of turmeric solution
${\mathrm{NH}}_4\mathrm{Cl}$	HCl (Strong)	${\mathrm{NH}}_4\mathrm{OH}$ (Weak)	Acidic	Red
$\mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2$	${\mathrm{HNO}}_3$ (Strong)	$\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$ (Weak)	Acidic	Yellow
NaCl	HCl (Strong)	NaOH (Strong)	Neutral	Yellow
$K_2{\mathrm{SO}}_4$	$H_2{\mathrm{SO}}_4$ (Strong)	KOH (Strong)	Neutral	Yellow
${\mathrm{Na}}_2{\mathrm{CO}}_3$	$H_2{\mathrm{CO}}_3$ (Weak)	NaOH (Strong)	Basic	Red