Question

100 ml of 0.2 M HCl are mixed with 100 ml of 0.2M $\text{C}{{\text{H}}_{\text{3}}}\text{COONa}$, the pH of the resulting solution would be nearly:
A. 1
B. 0.7
C. 2.875
D. 1.6

Answer 1

Hint: To solve this question we need to write down the equation of the reaction that is mentioned. Once we are done writing the equation, we need to know the formula for finding the pH. For knowing the concentration, it is very important to know the reactants and the products are mentioned in the question.

Complete step-by-step answer:
Let us first examine the quantities that are provided in the question.
According to the question, a total of 0.2 moles of ${{\text{H}}^{\text{+}}}$ions react with 0.2 moles of $\text{C}{{\text{H}}_{\text{3}}}\text{COONa}$. The product of the reaction is 0.2 moles of $\text{C}{{\text{H}}_{\text{3}}}\text{COOH}$ and water.
Now that we know the reactants and the products, let us first write down the equation of the chemical reaction. Here it is:
$\text{HCl + C}{{\text{H}}_{\text{3}}}\text{COONa }\xrightarrow{{}}\text{ C}{{\text{H}}_{\text{3}}}\text{COOH + NaCl}$
In the above mentioned reaction,
The concentration of HCl is 0.2M.
The concentration of $\text{C}{{\text{H}}_{\text{3}}}\text{COONa}$ is 0.2M.
The concentration of $\text{C}{{\text{H}}_{\text{3}}}\text{COOH}$ is 0.2M.
Now, we have to find the pH value.
So, $\text{pH = }-\text{ log ( 2 }\times \text{ 1}{{\text{0}}^{-\text{1}}}\text{)}$
Therefore, $\text{pH = }-\text{log 2 + log 10}$
This gives the answer as 0.698. This is approximately 0.7.
So, the correct answer to the question is Option B.

Note: The pH of any solution is based on the values of the pH scale. This scale has values ranging between 0 to 14. A pH of 7 signifies that the solution is neutral in nature. When the pH value is below 7 (that is between 0 to 6), the solution is acidic in nature. When the pH value is above 7 (that is between 8 to 14), the solution is basic in nature.