Question

For a particular reaction change in h is 67.7 kj and change in s is 126.9 j/k assuming these values change very little with temperature, at what temperature does the reaction change from non spontaneous to spontaneous

Answer 1

The reaction changes from nonspontaneous to spontaneous at approximately 420 K, calculated by setting the Gibbs free energy (ΔG) to zero and rearranging ΔG = ΔH - TΔS to solve for T with the provided values of ΔH and ΔS.

Step-by-step explanation:

The student is asking about the temperature at which a chemical reaction becomes spontaneous based on its thermodynamic properties. To determine this temperature, one must utilize Gibbs free energy (ΔG), which is calculated using the formula ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy. A reaction is spontaneous when ΔG is negative.

For a reaction to change from nonspontaneous to spontaneous, ΔG must equal zero. Using the given values for ΔH (67.7 kJ) and ΔS (126.9 J/K), one can rearrange the equation to solve for T, resulting in T = ΔH / ΔS. Note that ΔH must be converted to J by multiplying by 1000 to match the units of ΔS.

T = (67.7 kJ * 1000 J/kJ) / (126.9 J/K) = 53350 J / 126.9 J/K ≈ 420 K.

Therefore, the reaction will change from nonspontaneous to spontaneous at approximately 420 K.