Book: Key Terms: Ch. 20

Question 1

adenosine triphosphate (ATP)

Answer 1

.

Question 2

coupling of reactions

Answer 2

When two reactions are coupled, one step supplies enough free energy for the other to occur.

Question 3

entropy (S)

Answer 3

S = k ln(W), where k is the Boltzmann constant, and W is the number of microstates. Entropy describes the amount of disorder in a system.

Question 4

free energy (G)

Answer 4

G = H - T S, where H is enthalpy, S is entropy, and T is temperature in kelvin. The equation for the free energy of a reaction can be rewritten as ∆G = ∆H - T ∆S, and the change in the free energy is a measure of the spontaneity of a reaction. If ∆G < 0, it is spontaneous; if ∆G > 0, it isn’t. If ∆G = 0, the process is at equilibrium.

Question 5

microstate

Answer 5

Each quantized state of a system is called a microstate, and at any instant, the total energy of the system is dispersed throughout one microstate.

Question 6

second law of thermodynamics

Answer 6

All real processes occur spontaneously in the direction that increases the entropy of the universe (system + surroundings).

Question 7

spontaneous change

Answer 7

Spontaneous change of a system is one that occurs under specified conditions without a continuous input of energy from outside the system.

Question 8

standard entropy of reaction (∆Sº_rxn)

Answer 8

The entropy change that occurs when all the reactants and products are in their standard states. If there is an increase in moles of gas, ∆Sº_rxn > 0, and if there’s a decrease, ∆Sº_rxn < 0. The general equation for ∆Sº_rxn is given as:
∆Sº_rxn = m Σ Sº_products - n Σ Sº_reactants

Question 9

standard free energy change (∆Gº)

Answer 9

The standard free energy change of a reaction occurs when all of the components of the system are in their standard states: ∆Gº_sys = ∆Hº_sys - T ∆Sº_sys

Question 10

standard free energy of formation (∆Gº_f)

Answer 10

All substances have values for this. It is the energy change that occurs when 1 mol of a compound is made from its elements, with all components in their standard states. The general equation is:
∆Hº_rxn = m Σ Hº_(f)products - n Σ Hº_(f)reactants

Question 11

standard molar entropy (Sº)

Answer 11

A way of specifying the entropy of substances that takes into account the fact that entropy is an extensive property; Sº has units of J / mol K and it is typically given for a substance at 298 K with other std conditions.

Question 12

third law of thermodynamics

Answer 12

A perfect crystal has zero entropy at absolute zero: S_sys = 0 at 0 K.