Question: In a reaction where ΔH is negative and ΔS is positive, what can be said about ΔG?
Options:
ΔG is always negative.
ΔG is always positive.
ΔG is zero.
ΔG depends on temperature.
Correct Answer: ΔG is always negative.
Solution:
If ΔH is negative and ΔS is positive, ΔG will always be negative at all temperatures.
In a reaction where ΔH is negative and ΔS is positive, what can be said about ΔG
Practice Questions
Q1
In a reaction where ΔH is negative and ΔS is positive, what can be said about ΔG?
ΔG is always negative.
ΔG is always positive.
ΔG is zero.
ΔG depends on temperature.
Questions & Step-by-Step Solutions
In a reaction where ΔH is negative and ΔS is positive, what can be said about ΔG?
Step 1: Understand what ΔH means. ΔH (enthalpy change) being negative means the reaction releases heat (exothermic).
Step 2: Understand what ΔS means. ΔS (entropy change) being positive means the disorder of the system increases.
Step 3: Know the formula for ΔG. ΔG (Gibbs free energy change) is calculated using the formula ΔG = ΔH - TΔS, where T is the temperature in Kelvin.
Step 4: Since ΔH is negative, this part of the equation will lower ΔG.
Step 5: Since ΔS is positive, TΔS will be a positive value, but because ΔH is negative, it will still keep ΔG negative.
Step 6: Conclude that with ΔH negative and ΔS positive, ΔG will always be negative at all temperatures, indicating the reaction is spontaneous.
Gibbs Free Energy – The relationship between enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) is given by the equation ΔG = ΔH - TΔS. This concept tests the understanding of thermodynamic principles.
Thermodynamic Favorability – A negative ΔG indicates a spontaneous reaction. The conditions under which ΔG is negative depend on the signs of ΔH and ΔS.
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