Question

Find the valence factor for following acids
$\left(i\right)H_{3}P{O}_3$
$\left(ii\right)H_{3}B{O}_3$

• A. $\left(i\right)1or2$
  $\left(ii\right)1$
• B. $\left(i\right)1$
  $\left(ii\right)1or2$
• C. $\left(i\right)3$
  $\left(ii\right)3$
• D. None of the above

Answer 1

The correct option is A $\left(i\right)1or2$

$\left(ii\right)1$
In case of acid-base reaction, the valency factor is the actual number of $H^{+}$ or $O{H}^{-}$ replaced in the reaction. The acid or base may contain more number of replaceable $H^{+}$ or $O{H}^{-}$ than actually replaced in reaction.
valency factor for acid is the number of $H^{+}$ ion replaced by per molecule of the acid.
$H_{3}P{O}_3$ has 2 replacable $H^{+}$ hence it's valency can be 1 or 2.
and $H_{3}B{O}_3$ has 3 hydrogen linked to oxygen yet all are not replacable
$H_{3}B{O}_3+H_{2}O\to \left[B\right(OH{)}_4{]}^{-}+H_3{O}^{+}$ thus mole of boric acid can give only one $H^{+}$ ion hence valency factor is 1.