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Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium

Chapter 18, Problem 107

Compare the values of ∆G and ∆G° when: (a) Q < 1. (b) Q = 1. (c) Q > 1. Does the thermodynamic tendency for the reaction to occur increase or decrease as Q increases?

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Hello in this problem. We are asked which one of these statements about the changing give strategy under nonstandard conditions and that under standard conditions is correct. We are asked what happens to the thermodynamic tendency for the reaction to take place when the value of Q decreases. So let's begin by considering then the relationship between the change and gives you energy under nonstandard conditions to that under standard conditions. So it was provided by the equation. The changing gives you energy under nonstandard conditions equal to that under standard conditions, plus the gas constant times, temperature, times the natural log over reaction quotient. So let's start by considering A then So A says then that Q is greater than one. So that means that the change and gives you energy understand nonstandard conditions will be less than that under standard conditions because the R t l n f q is negative. So the R t l n f Q will actually be positive when Q is greater than one. This is because the natural log of a number greater than one is gonna be positive, so that's not correct. The next one then says that when Q is equal to one, the change and gives for energy under nonstandard conditions is equal to that under standard conditions because our T Ln of Q is equal to zero and this is correct. So the natural log of one is equal to zero. So statement B is a correct statement. And then if you consider C C says then that the reaction quotient is less than one the change and gives for energy under nonstandard conditions is greater than that under standard conditions, because R T L N F Q is positive. R t L n F Q will actually be negative when Q is less than one. That's because the natural log of a number less than one will be negative, So C. Is also not correct. Then last part asks us then what happens to the thermodynamic tendency for the reaction to take place from the value of Q decreases. So when our value of Q decreases, it means then the R. T. L. N. Of Q will also decrease. And that says then the change in gibbs free energy under nonstandard conditions will decrease. A decrease in the change in gibbs Free energy means an increase in the thermodynamic tendency. So decreasing Q will lead to an increase in the thermodynamic tendency. And again, this second statement is a correct statement because natural log of one is zero. So that means then when Q is equal to one, the change in gibbs free energy under nonstandard conditions will equal that under standard conditions. Thanks for watching. Hope, this help
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