Chemistry Thermochemistry PMC 2021
PMDC Verified Question 52 of 81
\( \Delta H \) for exothermic reaction is ____ ?
A
Neutral
B
Positive
C
Negative
D
More than 1
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Negative
Concept:

Thermochemical sign conventions dictate the flow of energy relative to the system. An exothermic reaction is a system that releases thermal energy to its surroundings.

Formula:

$$ \Delta H = H_{\text{products}} - H_{\text{reactants}} $$

Solution:

  • Because heat leaves the system, the internal enthalpy of the system decreases.


  • This means the final state (products) has less energy than the initial state (reactants).


  • Subtracting a larger initial value from a smaller final value yields a mathematically Negative result (\( \Delta H < 0 \)).


Why other options are incorrect:

Positive \( \Delta H \) indicates an endothermic process. "More than 1" and "Neutral" do not describe standard thermodynamic sign conventions.

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