Lecture 3: Energy and Entropy

Question 1

What is entropy?

Answer 1

Entropy, S = Kb ln(W)
where W is the number of microstates corresponding to a particular macrostate and Kb is the Boltzmann constant.

W is proportional to V^n
When n = number of molecules/particles

Question 2

Complete the equation: deltaS = …. and give the conditions in which this equation is true.

Answer 2

DeltaS = delta q/T

in a closed system, at constant temperature

Question 3

What is the equation involving deltaS(universe)?

Answer 3

deltaS(universe) = deltaS(system) + deltaS(surroundings)

For a spontaneous, deltaS(universe) is positive

Question 4

What is Gibbs free energy?

Answer 4

G = H - TS

If delta G is negative, the reactions is spontaneous.

Question 5

Explain how G = H - TS is linked to entropy-driven or enthalpy-driven reactions.

Answer 5

If delta H is -ve —> enthalpy driven
If -T(delta)S is -ve —> entropy driven
Can be both, but can’t be neither (then wouldn’t be spontaneous).

Question 6

What is the biochemical standard state?

Answer 6

1 M, 25 degrees C, pH 7