Question

Assertion: pH of $HCl$ solution is less than that of acetic acid of the same concentration
Reason: In equimolar solution, the number of titratable protons present in HCI is less than that present in acetic acid
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Assertion is incorrect but Reason is correct.
E. Both Assertion and Reason are incorrect.

Answer 1

Hint: pH is a scale used to specify the acidity or basicity of a solution. Acids or acidic solutions have lower pH values than bases or basic solutions. Strong acids will have pH values less than weak acids. Hydrochloric acid is a stronger acid compared to acetic acid. The lower the pH value, the higher is the concentration of hydrogen ions (protons) in the solution. Use this info to state whether the assertion and reason are correct or not.

Complete step by step solution: Concentration of an acid is a measure of the amount of acid ions dissolved in a solvent.
Hydrochloric acid ($HCl$) is a stronger acid than acetic acid ($C{H_3}COOH$).
Here, when the concentrations of $C{H_3}COOH$ and $HCl$ are the same, the pH of $HCl$ will definitely be less than that of $C{H_3}COOH$ as $HCl$ is a stronger acid.
Therefore, the given assertion is correct.
Equimolar solution is a solution where the no. of solute particles of different compounds is the same.
When equal amounts of $HCl$ and $C{H_3}COOH$ are dissolved in a solution, then the no. of titratable protons present in $HCl$ is greater than that of $C{H_3}COOH$. Because as $HCl$ is a stronger acid, it will produce more no. of protons (hydrogen ions ${H^ + }$) than $C{H_3}COOH$. Hydrogen ion concentration is higher in $HCl$ than in acetic acid.
Therefore, the given reason is incorrect.
Assertion is correct but reason is incorrect.

Hence, the correct option is Option C.

Note: Assertion means a statement and reason is the explanation about that particular statement. You have to find out whether each statement is correct or not. If both the statements are correct, you have to find out whether the reason supports the assertion or not. Do not confuse in answering these types of questions. “Equimolar” is the same as “same concentration”.