If a reaction has ΔH < 0 and ΔS > 0, the process is spontaneous:

• A. Spontaneous at all temperatures
• B. Spontaneous only at high temperatures
• C. Spontaneous only at low temperatures
• D. Never spontaneous

Answer: (A)

The key idea is that spontaneity is determined by Gibbs free energy, ΔG = ΔH − TΔS. A reaction is spontaneous when ΔG < 0. Here ΔH is negative (releases heat) and ΔS is positive (increases disorder). That means both terms push ΔG downward: the enthalpy term is already negative, and subtracting TΔS with ΔS positive makes ΔG even more negative as temperature rises. So for any positive temperature, ΔG remains negative, and the process is spontaneous at all temperatures (even at very low temperatures, where ΔG still equals ΔH). This is why the other options don’t apply: there isn’t a temperature range where spontaneity would disappear.