Question

The pH of an aqueous solution of ${{\text{H}}_2}{{\text{O}}_2}$ is $6.0$. Some chlorine is bubbled through this solution. The pH of the resulting solution will be:
A. $6$
B. $7$
C. less than $6$
D. more than $7$

Answer 1

Hint: pH is a unit of measure which describes the degree of acidity or alkalinity of a solution. It is measured on a scale of $0 - 14$. Low pH values correspond to high concentrations of ${{\text{H}}^ + }$ and high pH values correspond to low concentrations of ${{\text{H}}^ + }$.

Complete step by step answer:
The pH value of a substance is directly related to the ratio of the hydrogen ion and hydroxyl ion concentrations. If the ${{\text{H}}^ + }$ concentration is higher than ${\text{O}}{{\text{H}}^ - }$, the material is acidic. If the ${\text{O}}{{\text{H}}^ - }$ concentration is higher than ${{\text{H}}^ + }$, the material is basic.
Acid is any compound which forms ${{\text{H}}^ + }$ ions in solution. It is also known as proton donors. Base is any compound which combines with ${{\text{H}}^ + }$ in solution. It is also known as proton acceptors.
When ${{\text{H}}_2}{{\text{O}}_2}$ is reacted with chlorine gas, it produces hydrochloric acid and oxygen gas. The corresponding reaction is given below:
${{\text{H}}_2}{{\text{O}}_2} + {\text{C}}{{\text{l}}_2} \to 2{\text{HCl}} + {{\text{O}}_2}$
This reaction increases the ${{\text{H}}^ + }$ ion concentration, i.e. the product formed is an acid. We know that acids have pH values less than $7$.
From the options given above, the apt answer will be less than $6$.

So the correct option is C.

Note:
The p in pH stands for potenz meaning power and H stands for hydrogen. The pH scale starts with a zero pH, i.e. hydrogen ion concentration is $1$. It means the solution is strongly acidic. At the other end of scale, pH is $14$, i.e. hydrogen ion concentration is ${10^{ - 14}}$. It means the solution is alkaline. The central point pH in the scale is $7$, because $\left[ {{{\text{H}}_3}{{\text{O}}^ + }} \right]$ is equal to $\left[ {{\text{O}}{{\text{H}}^ - }} \right]$, i.e. hydrogen ion concentration is ${10^{ - 7}}$.