Question

The hydrogen ion concentration and pH of the solution obtained by mixing 100ml of 1.0M HNO3 with 100ml of 0.8M KOH is, how do we solve this?

Answer 1

For a mixture of strong acid and base,

Check the no of moles of acid and base present. Here, 100 milli moles of HNO₃ and 80 millimoles of KOH is present. Since the H+ ion concentration is more than OH- ion concentration,

i.e.

$[H^{+} ] = \frac{[H^{+}]_{1}V_{1} - [OH^{-}]_{2}V_{2} }{V_{1} +V_{2}}$

$= \frac{1 * 100 - 0.8*100}{200} \\= \frac{20}{200} \\= 0.1$

This is the hydrogen ion conc.

pH = -log[H⁺]

pH = 1

( In some questions, the moles of base given will be greater than the moles of acid, then the formula is: )

$[OH^{-} ] = \frac{[OH^{-}]_{1}V_{1} - [H^{+}]_{2}V_{2} }{V_{1} +V_{2}}$