KVPY SA Exam 2018 Question Paper

Question : 32 of 80

Marks: +1, -0

Among the following, the correct statement is

pH decreases when solid ammonium chloride is added to a dilute aqueous solution of NH $_3$
pH decreases when solid sodium acetate is added to dilute aqueous solution of acetic acid
pH decreases when solid NaCl added to a dilute aqueous solution of NaOH
pH decreases when solid sodium oxalate is added to a dilute aqueous solution of oxalic acid

Solution:

Dil aqueous Solution of

NH_3

NH_4OH

solution

NH_4OH ⇌ NH^{+}4 +O↖{-}H

On adding solid ammonium chloride

NH_4 ⇌ NH_4 ^{+} +Cl^{–}

The reaction moves backward due to common ion effect. The concentration of OH– decreases and pH decressess.

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