Calculate the change in Gibbs free energy for each of the sets of ΔHrxn, ΔSrxn, and T given in P

Calculate the change in Gibbs free energy for each of the...

Key Concepts

Gibbs Free Energy Equation (?G = ?H - T?S)

This fundamental equation links enthalpy, entropy, and temperature to predict the spontaneity of reactions. A reaction is spontaneous if ?G is negative, meaning the combination of energy changes (enthalpy and entropy) at the given temperature favors the process occurring naturally.

Temperature Dependence

Temperature plays a critical role in determining reaction spontaneity since it scales the contribution of the entropy term (T?S) in the Gibbs free energy equation. Changing the temperature can shift the balance between enthalpy and entropy, thereby influencing whether the reaction is spontaneous.

Gibbs Free Energy

Gibbs free energy is a thermodynamic quantity that combines enthalpy and entropy to determine the spontaneity of a process. It provides a criterion for spontaneity at constant temperature and pressure, indicating whether a reaction can proceed without external work.

Enthalpy Change (?H)

Enthalpy change represents the total heat absorbed or released during a chemical reaction at constant pressure. A negative ?H indicates an exothermic reaction, which can favor spontaneity, although the net effect depends on the accompanying entropy change.

Entropy Change (?S)

Entropy change measures the degree of randomness or disorder in a system during a reaction. A positive ?S means that the system becomes more disordered, which can contribute to making a reaction spontaneous, particularly at higher temperatures.

Transcript

00:01 In this question, we're going to be looking at the standard gibbs enthalpy change, gives energy change, which by definition is given as the standard enthalpy change, minus t, the standard enthalpy change, the standard entropy change.

00:14 So this is the formula that we're going to be applying in all the cases.

00:17 For example, for the first system where we have our, we're going to say the standard gibbs energy change is equal to the standard enthalpy change of negative 95 times 10 to the power 3, and this is in jolts minus the temperature of 298 kelvin multiplied by the standard entropy change of 157 joules per kelvin.

00:39 So if we calculate this, the standard gives energy change is going to be negative for 8 times 10 to the power 4 joules.

00:56 So we can conclude here to say this standard gives energy change is going to be equal to negative.

01:06 4 8 kilojoules.

01:08 If we notice this, this value is less than 0.

01:11 So we can conclude that this reaction is spontaneous.

01:17 It spontaneous at 298 kelvin.

01:21 So we always have to make sure that we are making reference to say it's spontaneous at this particular temperature.

01:28 Because if this temperature is, for example, very low or very large, this temperature can change in such a way that the overall gives energy change is going to be a positive value so we always have to make reference to the temperature to say if we look at the gibbs energy change the standard gibbs energy change at a temperature of 298 it is less than zero so this reaction is spontaneous at 298 kelvin so moving on to the next systems we're going to calculate the gibbs energy change being equal to negative 95 times 10 to the power 3 jols my minus 855 multiplied by negative 157.

02:11 So the standard gives energy change here is going to be equal to 39 kilojoules...

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