Calculate the ph of a solution formed by mixing 200.0 ml of 0.30 m hclo with 300.0 ml of 0.20 m kclo. the ka for hclo is 2.9 × 1

Question

Akimi4 [234]

3 years ago

7

Calculate the ph of a solution formed by mixing 200.0 ml of 0.30 m hclo with 300.0 ml of 0.20 m kclo. the ka for hclo is 2.9 × 1

0-8.

Chemistry

2 answers:

Kaylis [27] · Answer 1 · 2022-02-18T03:37:00+03:00

The pH of the solution formed by mixing 200 mL of 0.3 M HClO with 300 mL of 0.2 M KClO is $\boxed{7.537}$ .

Further Explanation:

Buffer solution:

An aqueous solution that contains a weak acid and its conjugate base is termed as a buffer solution. It resists any change in its pH on addition of strong acid or base.

Types of buffers solutions:

1. Acidic buffer: These are the solutions with a pH of less than 7. It contains a weak acid and its conjugate base. A mixture of acetic acid and sodium acetate is an example of an acidic buffer.

2. Basic or alkaline buffer: These are the solutions with a pH more than 7. It contains a weak base and its conjugate acid. A mixture of ammonium chloride and ammonium hydroxide is an example of a basic or alkaline buffer.

The given solution is an acidic buffer of weak acid HClO and salt KClO.

The molarity of HClO is 0.30 M. It means its concentration is 0.30 M in 1 L of solution. So the concentration of HClO in 200 mL solution is calculated as follows:

$\begin{aligned}{\text{Concentration of HClO}}&= \left({{\text{0}}{\text{.30 M}}} \right)\left( {200{\text{ mL}}} \right)\left( {\frac{{{\text{1}}{{\text{0}}^{ - 3}}{\text{ L}}}}{{1{\text{ mL}}}}} \right)\\&= 0.06{\text{ M}}\\\end{aligned}$

The molarity of KClO is 0.20 M. It means its concentration is 0.20 M in 1 L of solution. So the concentration of KClO in 300 mL solution is calculated as follows:

$\begin{aligned}{\text{Concentration of KClO}} &= \left( {{\text{0}}{\text{.20 M}}} \right)\left( {300{\text{ mL}}}\right)\left( {\frac{{{\text{1}}{{\text{0}}^{ - 3}}{\text{ L}}}}{{1{\text{ mL}}}}} \right)\\&= 0.06{\text{ M}}\\\end{aligned}$

Henderson-Hasselbalch equation is a mathematical expression that is used to calculate the of buffer solutions. Its equation for the given buffer solution is as follows:

${\text{pH}} ={\text{p}}{{\text{K}}_{\text{a}}} +\log \dfrac{{\left[ {{\text{KClO}}} \right]}}{{\left[ {{\text{HClO}}} \right]}}$ …… (1)

Here,

${\text{p}}{{\text{K}}_{\text{a}}}$ is the negative logarithm of acid dissociation constant.

pH is the negative logarithm of hydrogen ion concentration.

$\left[ {{\text{KClO}}} \right]$ is the concentration of salt, KClO.

$\left[ {{\text{HClO}}} \right]$ is the concentration of acid, HClO.

The formula to calculate ${\text{p}}{{\text{K}}_{\text{a}}}$ is as follows:

${\text{p}}{{\text{K}}_{\text{a}}} = - \log {{\text{K}}_{\text{a}}}$ …… (2)

Here,

${{\text{K}}_{\text{a}}}$ is the dissociation constant of HClO.

The value of ${{\text{K}}_{\text{a}}}$ is $2.9 \times {10^{ - 8}}$ .

Substitute this value in equation (2).

$\begin{aligned}{\text{p}}{{\text{K}}_{\text{a}}}&=- \log \left({2.9 \times {{10}^{ - 8}}} \right)\\&= 7.537\\\end{aligned}$

The value of ${\text{p}}{{\text{K}}_{\text{a}}}$ is 7.537.

The value of $\left[ {{\text{KClO}}} \right]$ is 0.06 M.

The value of $\left[ {{\text{HClO}}} \right]$ is 0.06 M.

Substitute these values in equation (1).

$\begin{aligned}{\text{pH}}&= {\text{7}}{\text{.537}} + \log \frac{{\left( {0.06{\text{ M}}} \right)}}{{\left( {0.06{\text{ M}}} \right)}}\\&= 7.537+0\\&= 7.537\\\end{aligned}$