Question

The tribasic acid is

• A. ${\mathrm{H}}_3{\mathrm{PO}}_4$
• B. ${\mathrm{H}}_3{\mathrm{PO}}_3$
• C. ${\mathrm{H}}_3{\mathrm{PO}}_2$
• D. ${\mathrm{HPO}}_3$

Answer 1

The correct option is A

${\mathrm{H}}_3{\mathrm{PO}}_4$

The explanation for correct option:-

a) ${\mathrm{H}}_3{\mathrm{PO}}_4$

• An acid that can donate three hydrogen ions to a base in a reaction is called a tribasic acid
• Since P-H bonds are strong and are not ionic so they are not ionizable
• O-H bonds are ionizable and hence these hydrogen ions can be donated
• In the case of ${\mathrm{H}}_3{\mathrm{PO}}_4$, we have 3 $\mathrm{P}-\mathrm{OH}$ bonds which means three hydrogen ions can be donated and hence it is a tribasic acid.

The explanation for incorrect options:-

b) ${\mathrm{H}}_3{\mathrm{PO}}_3$

• In the case of ${\mathrm{H}}_3{\mathrm{PO}}_3$, we have two $\mathrm{P}-\mathrm{OH}$ bonds which means two hydrogen ions can be donated and hence it is a dibasic acid.

c) ${\mathrm{H}}_3{\mathrm{PO}}_2$

• In the case of ${\mathrm{H}}_3{\mathrm{PO}}_2$, we have one $\mathrm{P}-\mathrm{OH}$ bond which means only one hydrogen ion can be donated and hence it is a monobasic acid.

d) ${\mathrm{HPO}}_3$

• In the case of ${\mathrm{HPO}}_3$, we have one $\mathrm{P}-\mathrm{OH}$ bond which means only one hydrogen ion can be donated and hence it is a monobasic acid.

Therefore the correct option is a)${\mathrm{H}}_3{\mathrm{PO}}_4$