Determine ΔG in kJ at a temperature of 261 K given ΔHrxn = 91 kJ and ΔSrxn = 151 J/K.
To determine ΔG (the change in Gibbs free energy) at a given temperature, you can use the equation:
ΔG = ΔH - TΔS
where:
ΔG is the change in Gibbs free energy
ΔH is the change in enthalpy
T is the temperature in Kelvin
ΔS is the change in entropy
In this case, the given values are:
ΔHrxn = 91 kJ
ΔSrxn = 151 J/K
T = 261 K
Now, let's convert the given values to the appropriate units before substituting them into the equation:
ΔHrxn = 91 kJ = 91,000 J (since 1 kJ = 1000 J)
ΔSrxn = 151 J/K (no conversion needed)
Now, substitute the values into the equation:
ΔG = (91,000 J) - (261 K)(151 J/K)
Multiplying the units:
ΔG = 91,000 J - 39,411 J
Finally, perform the subtraction:
ΔG = 51,589 J
To convert J to kJ, divide by 1000:
ΔG = 51.589 kJ
Therefore, ΔG at a temperature of 261 K is 51.589 kJ.