Problem

The pair of compounds which cannot exist together in aqueous solution is : (I)

\text{NaH}_2\text{PO}_4

and

\text{NaHCO}_3

(II)

\text{Na}_2\text{CO}_3

and

\text{NaHCO}_3

(III)

\text{NaOH}

and

\text{NaH}_2\text{PO}_2

(IV)

\text{NaHCO}_3

and

\text{NaOH}

a. I, II, III b. II, III c. III, IV d. only IV