Chemistry Equilibrium MDCAT 2014
PMDC Verified Question 96 of 102
What will be the pH of a solution of \( \text{NaOH} \) with a concentration of \( 10^{-3} \) M?
A
3
B
11
C
14
D
7
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 11
Concept:

\( \text{NaOH} \) is a strong base that completely dissociates in water. The relationship between pH and pOH must be used.

Formula:

$$ \text{pOH} = -\log[\text{OH}^-] $$

$$ \text{pH} + \text{pOH} = 14 $$

Solution:

  • Since \( \text{NaOH} \) is a strong base, \( [\text{OH}^-] = [\text{NaOH}] = 10^{-3} \text{ M} \).


  • Calculate pOH: \( \text{pOH} = -\log(10^{-3}) = 3 \).


  • Calculate pH: \( \text{pH} = 14 - \text{pOH} \).


  • \( \text{pH} = 14 - 3 = 11 \).


Why other options are incorrect:

Option A (3) is the pOH, not the pH, representing an acidic solution which is impossible for NaOH. Options 7 and 14 are standard pH reference points but mathematically incorrect for this concentration.

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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