Chemistry Alcohols & Phenols MDCAT 2010
PMDC Verified Question 95 of 95
Dissociation constant of phenol is:
A
\(1.2 \times 10^{-10}\)
B
\(1.2 \times 10^{10}\)
C
\(1.3 \times 10^{10}\)
D
\(1.3 \times 10^{-10}\)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: \(1.3 \times 10^{-10}\)
Concept:

The acid dissociation constant (\(K_a\)) quantifies the extent of acid dissociation in water. Phenol is a weak acid, meaning its \(K_a\) is very small.

Formula:

$$ K_a = \frac{[\text{H}^+][\text{C}_6\text{H}_5\text{O}^-]}{[\text{C}_6\text{H}_5\text{OH}]} $$

Solution:

  • The accepted experimental \(K_a\) value for phenol at 25°C is \(1.3 \times 10^{-10}\).


Why other options are incorrect:

Options with positive exponents (\(10^{10}\)) indicate a superacid, which is logically impossible for phenol. \(1.2 \times 10^{-10}\) is numerically incorrect according to standard curriculum data.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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