Thermodynamics

Question 1

What is the first law of thermodynamics?

Answer 1

Energy cannot be created or destroyed, only converted from one form to another

Question 2

Define work

Answer 2

Any process that can be used to lift weight

Question 3

What is work measured in?

Answer 3

Joules

Question 4

Define heat

Answer 4

The spontaneous transfer of energy from a region of high tempature to a region of lower temperature

Question 5

What is heat measured in?

Answer 5

Joules

Question 6

Define temperature

Answer 6

A measure of themal energy of a system, the ability of a system to transfer heat energy to another system

Question 7

What is enthalpy measured in?

Answer 7

Joules per mole

Question 8

What is true of enthalpy change if a reaction involves no change in pressure or volume?

Answer 8

Change in enthalpy is the same as the change in internal energy

Question 9

Define entropy

Answer 9

The measure if distribution of energy throughout the atoms and molecules that make up a system

Question 10

What is entropy measured in?

Answer 10

Joules per mole per kelvin

Question 11

What is the second law of thermodynamics?

Answer 11

Any system which is free of external influences becomes more disordered with time

Question 12

Explain the role of entropy in protein folding

Answer 12

• When a protein chain folds, the solvating water molecules become more disorganised
• This offsets any decrease in entropy due to folding of the protein into a more organised structure
• Net change in entropy is positive

Question 13

What is Gibbs free energy?

Answer 13

The portion of the enthalpy of a reaction that is avaliable to do work

Question 14

What are the units of Gibbs free energy?

Answer 14

Joules per mol

Question 15

What is an exergonic reaction?

Answer 15

A reaction which releases energy to its surroundings

Question 16

What is an endergonic reaction?

Answer 16

A reaction which absorbs energy from its surroundings

Question 17

Are exergonic reactions spontaneous?

Answer 17

Yes

Question 18

What does ΔGº mean?

Answer 18

Free energy chage under standard conditions

Question 19

What does ΔGº’ mean?

Answer 19

Free energy change under standard conditions at pH 7

Question 20

How does your body ensure that energy in reactions isn’t just lost as heat?

Answer 20

Energy-releasing chemical reactions are coupled to energy-requiring reactions

Question 21

When might ΔGº’ be used rather than ΔGº in a calculation?

Answer 21

If a reaction involves the uptake or release of protons

Question 22

What does ΔG’ represent?

Answer 22

The free energy change associated with a reaction at pH 7 but not under standard conditions

Question 23

What assumption is made in calculation of ΔG’?

Answer 23

The pH does not devaite from 7 as the reaction proceeds

Question 24

How can free energy of a reverse reaction be obtained?

Answer 24

By changing the sign

Question 25

How is the ΔG for a reaction calculated?

Answer 25

G_products-G_reactants

Question 26

What does the ΔG tell you about the rate of a reaction?

Answer 26

• Whether a reaction is spontaneous
• Nothing about the rate

Question 27

What does Kc describe?

Answer 27

The ratio of the concentrations of the products to those reactants when equilibrium has been reached

Question 28

What units should concentrations be in to calculate Kc?

Answer 28

mol.L^-1

Question 29

What does a value of Kc above 10² indicate?

Answer 29

The reaction lies to the right with the products favoured over the reactants

Question 30

What does a value of kc between 10² to 10^-2?

Answer 30

The reaction lies towards the centre

Question 31

What does a value of Kc below 10^-2 indicate about a reaction?

Answer 31

The reaction lies to the left, favouring reactants

Question 32

What does a ΔG of 0 represent?

Answer 32

That a reaction is at thermodynamic equilibrium