Question

A weak monobasic acid is \(18\) % dissociated in \(0.05\) M solution. Calculate the concentration of solution if it is \(10\) % dissociated .

• A. \(0.162\) M.
• B. \(0.141\) M.
• C. \(0.184\) M.
• D. \(0.125\) M.

Hint:

Keep the dissociation constant fixed and use K = c alpha squared to compare the two solutions.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
For a weak monobasic acid, the dissociation constant is \(K_a = c\alpha^2\) (for small \(\alpha\)). It stays constant at a given temperature.

Step 2: Equate the Two Cases
\(c_1\alpha_1^2 = c_2\alpha_2^2\)
\(0.05 \times (0.18)^2 = c_2 \times (0.10)^2\)

Step 3: Calculation
\(c_2 = \dfrac{0.05 \times 0.0324}{0.01} = 0.162\) M

Step 4: Compare the options
The concentration is \(0.162\) M, option (A).

Final Answer:
The solution would have a concentration of 0.162 M. \[ \boxed{\text{(A) }\text{0.162 M.}} \]