Question

$p K_{a}$ values of some phenols and ethanol are given in table.

Compound	Formula	$pK_a$
$o$-nitrophenol	$o- O _{2} N - C _{6} H _{4}- OH$	$7.2$
$p$-nitrophenol	$p- O _{2} N - C _{6} H _{4}- OH$	$7.1$
phenol	$C _{6} H _{5}- OH$	$10.0$
ethanol	$C _{2} H _{5} OH$	$15.9$

Select the incorrect statement(s) from the above table.

• A. The greater the $p K_{a}$ value, stronger is the acid
• B. Phenol is million times more acidic than ethanol
• C. Phenol is less acidic the $o$-nitrophenols
• D. $o$-and $p$-nitrophenol have nearly the equal acidic strength

Answer 1

Answer: (A)

Since, $p K_{a}=-\log K_{a}$ and $K_{a}$ is the measure of acidic strength. So, greater the $p K_{a}$ value, weaker is the acid.