In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?
Practice Questions
1 question
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
At high temperatures, ΔG will be positive because the positive ΔH and negative ΔS will dominate the equation ΔG = ΔH - TΔS.
Questions & Step-by-step Solutions
1 item
Q
Q: In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?
Solution: At high temperatures, ΔG will be positive because the positive ΔH and negative ΔS will dominate the equation ΔG = ΔH - TΔS.
Steps: 7
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.
