The pH of 0.1 M solution of the following salts increases in the...

HCl: Strong acid (low pH)
$N{H}_{4}Cl$ : Salt of weak base + strong acid → it gives acidic solution. (pH less than 7)
NaCl: Salt of strong base + strong base → it gives neutral solution with pH $= 7. <br/>NaCl: Salt of strong base + weak acid → it gives basic solution with pH > 7. <br/>Thus the increasing order of pH is <br/>$HCl < N{H}_{4}Cl < NaCl < NaCN