question_answer

Arrange the following in increasing order of \[pH\,\,KN{{O}_{3}}(aq),\,C{{H}_{3}}COON(aq),\]\[N{{H}_{4}}Cl(aq),\,{{C}_{6}}{{H}_{5}}COON{{H}_{4}}(aq)\]

A) \[C{{H}_{3}}COONa<{{C}_{6}}{{H}_{5}}COON{{H}_{4}}\]\[<N{{H}_{4}}Cl<KN{{O}_{3}}\]

B) \[KN{{O}_{3}}<N{{H}_{4}}C<C{{H}_{3}}COONa\]\[<{{C}_{6}}{{H}_{5}}COONa\]

C) \[N{{H}_{4}}Cl<KN{{O}_{3}}<C{{H}_{3}}COONa\]\[<{{C}_{6}}{{H}_{5}}COON{{H}_{4}}\]

D) \[N{{H}_{4}}Cl<KN{{O}_{3}}<{{C}_{6}}{{H}_{5}}COON{{H}_{4}}\]\[<C{{H}_{3}}COONa\]

Correct Answer: D

Solution :

[d] (i) \[KN{{O}_{3}}\] is a salt of strong acid and strong base, hence its aqueous solution is neutral; pH = 7

(ii) \[C{{H}_{3}}COONa\] is a salt of weak acid and strong base/hence, its aqueous solution is basic ; pH > 7

(iii) \[N{{H}_{4}}Cl\] is a salt of strong acid and weak base, hence its aqueous solution is acidic; pH < 7

(iv) \[{{C}_{6}}{{H}_{5}}COON{{H}_{4}}\] is a salt of weak acid, \[{{C}_{6}}{{H}_{5}}COOH\] and weak base, \[N{{H}_{4}}OH\]. But \[N{{H}_{4}}OH\] is slightly stronger than \[{{C}_{6}}{{H}_{5}}COOH\]. Hence, pH is slightly > 7.

Therefore, increasing order of pH of the given salts is

\[<C{{H}_{3}}COONa\]