Which of the following reactions is spontaneous at all temperatures?
Practice Questions
Q1
Which of the following reactions is spontaneous at all temperatures?
ΔH < 0 and ΔS < 0
ΔH > 0 and ΔS > 0
ΔH < 0 and ΔS > 0
ΔH > 0 and ΔS < 0
Questions & Step-by-Step Solutions
Which of the following reactions is spontaneous at all temperatures?
Correct Answer: A reaction with ΔH < 0 and ΔS > 0
Step 1: Understand the terms ΔH, ΔS, and ΔG. ΔH is the change in enthalpy (heat content), ΔS is the change in entropy (disorder), and ΔG is the change in Gibbs free energy.
Step 2: Know that a reaction is spontaneous if ΔG is negative.
Step 3: Remember the formula for ΔG: ΔG = ΔH - TΔS, where T is the temperature in Kelvin.
Step 4: Identify the conditions for spontaneity: If ΔH is less than 0 (ΔH < 0), it means the reaction releases heat (exothermic). If ΔS is greater than 0 (ΔS > 0), it means the reaction increases disorder.
Step 5: Analyze the formula: If ΔH < 0 and ΔS > 0, then as temperature (T) increases, the term TΔS also increases, but since ΔH is negative, ΔG will always remain negative.
Step 6: Conclude that a reaction with ΔH < 0 and ΔS > 0 will always have a negative ΔG, making it spontaneous at all temperatures.
