In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at

₹0.0

Question: In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?

Options:

Correct Answer: Positive

Solution:

At high temperatures, ΔG will be positive because the positive ΔH and negative ΔS will dominate the equation ΔG = ΔH - TΔS.

In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?

In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?

Step 1: Understand the symbols. ΔH represents the change in enthalpy (heat content), ΔS represents the change in entropy (disorder), and ΔG represents the change in Gibbs free energy.
Step 2: Identify the signs of ΔH and ΔS. In this case, ΔH is positive (meaning the reaction absorbs heat) and ΔS is negative (meaning the disorder decreases).
Step 3: Recall the equation for Gibbs free energy: ΔG = ΔH - TΔS, where T is the temperature in Kelvin.
Step 4: Consider what happens at high temperatures. As temperature (T) increases, the term TΔS becomes more significant.
Step 5: Since ΔS is negative, TΔS will also be negative (because a positive temperature multiplied by a negative ΔS gives a negative result).
Step 6: Now, substitute the signs into the equation: ΔG = positive ΔH - negative TΔS. This means ΔG = positive ΔH + positive value (from -TΔS).
Step 7: Since both terms in the equation are positive, ΔG will be positive at high temperatures.

Gibbs Free Energy – Understanding the relationship between enthalpy (ΔH), entropy (ΔS), and temperature (T) in determining the spontaneity of a reaction through the equation ΔG = ΔH - TΔS.
Thermodynamic Sign Conventions – Recognizing the implications of positive and negative values of ΔH and ΔS on the Gibbs free energy change (ΔG) and the conditions under which a reaction is spontaneous.