Question

Formic acid is a weak acid and hydrochloric acid is a strong acid. It follows that the:

• A. $\left[O{H}^{-}\right]of0.01MHCl(aq.)$ will be less than that of $0.01MHCOOH(aq.)$
• B. solution containing $0.1MNaOH(aq.)$ and $0.1MHCOONa(aq.)$ is a buffer solution
• C. $pH$ of ${10}^{-9}MHCl(aq.)$ will be approximately $7$ at ${25}^{\circ }C$
• D. $pH$ of a solution formed by mixing equimolar quantities of $HCOOH$ and $HCl$ will be less than that of a similar solution formed from $HCOOH$ and $HCOONa$

Answer 1

Answer: (A), (C), (D)

$\left[O{H}^{-}\right]of0.01MHCl(aq.)$ will be less than that of $0.01MHCOOH(aq.)$
$pH$ of ${10}^{-9}MHCl(aq.)$ will be approximately $7$ at ${25}^{\circ }C$
$pH$ of a solution formed by mixing equimolar quantities of $HCOOH$ and $HCl$ will be less than that of a similar solution formed from $HCOOH$ and $HCOONa$

As hydroxide ion and hydrogen ion's concentration is constant $\left[H^{+}\right]\times \left[O{H}^{-}\right]=C$ and formic acid is a weak acid (lower conc. of hydrogen ion) and hydrochloric acid is a strong acid (higher conc. of hydrogen ion) so hydroxide ion concentration of formic acid solution is high. As $HCl$ is acid so at lower concentration hydrogen ion contribution from water is considered and it will have approximately 7 $pH$ at ${25}^{o}C$.