Question

What is the pH of a 1.9 M solution of HClO4?

Answer 1

The compound HClO4 is said to be a strong acid which means it completely dissociates into the solution forming ions of hydrogen and perchlorate ion. 

HClO4 = H+ + ClO4-

pH = -log [H+]
pH = - log [1.9]
pH = -0.28

Answer 2

Answer : The pH of the solution is, -0.279

Explanation :

The balanced chemical reaction will be:

$HClO_4\rightleftharpoons H^++ClO_4^-$

As, 1 mole of $HClO_4$ dissociated in solution to give 1 mole of $H^+$ ion and 1 mole of $ClO_4^-$ ion

So, 1.9 M of $HClO_4$ dissociated in solution to give 1.9 M of $H^+$ ion and 1.9 M of $ClO_4^-$ ion

Now we have to calculate the pH of the solution.

$pH=-\log [H^+]$

$pH=-\log (1.9)$

$pH=-0.279$

As we know that the strong acid with concentration greater than 1 M will have the negative pH.

Therefore, the pH of the solution is, -0.279