In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at
Practice Questions
Q1
In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?
Positive
Negative
Zero
Cannot be determined
Questions & Step-by-Step Solutions
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.
