Chemistry Thermochemistry PMDC 2020
PMDC Verified Question 56 of 81
One calorie is equal to:
A
\( 0.418 \text{ KJ mol}^{-1} \)
B
\( 0.418 \text{ KJ} \)
C
\( 4.18 \text{ J} \)
D
\( 4.18 \text{ KJ} \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: \( 4.18 \text{ J} \)
Concept:

The calorie (cal) is a historical unit of energy defined as the amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius. The Joule (J) is the SI unit of energy.

Formula:

$$ 1 \text{ cal} = 4.184 \text{ Joules} $$

Solution:

  • By international thermochemical agreement, 1 standard calorie is precisely equivalent to 4.184 J.


  • Looking at the options, \( 4.18 \text{ J} \) is the correct rounded value matching this conversion factor.


Why other options are incorrect:

Option D (4.18 KJ) is 4180 Joules (which is a food Calorie or kilocalorie, not a standard calorie). Options A and B mistakenly use kilojoules with decimal placements that do not match the fundamental 1 cal = 4.18 J relation.

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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