Thermodynamics

Question 1

What are the 3 stores of internal energy (U)

Answer 1

Chemical bond storage

Between molecules (H bonds)

Kinetic energy = motion store

Question 2

What is temperature identical to in thermodynamics

Answer 2

Kinetic energy of a particle

Question 3

What does exothermic reaction mean in terms of internal energy of reactants and products

Answer 3

Reactants have more Internal energy = -ve U change

Question 4

What reaction shows a +internal energy change (products have more Internal energy)

Answer 4

Endothermic reaction

Question 5

What is the 1st law of thermodynamics

Answer 5

The energy released by a chemical reaction either is used to transfer heat or to do work on surroundings

Question 6

How would you measure internal energy change?

Answer 6

Measuring heat released (due to the chemical reactions internal energy)

Question 7

What is enthalpy

Answer 7

It is the heat released = enthalpy of a reaction

Question 8

How do you work out enthalpy change of a reaction? And the sign

Answer 8

Triangle H = enthalpy change

Energy released - work done = enthalpy change

Question 9

Why is enthalpy change (H)used more than internal energy (U) change

Answer 9

1- easier to measure than internal energy

2- enthalpy is used to measure Gibbs free energy

Question 10

What would positive or negative enthalpy (H) change mean?

Answer 10

The heat is absorbed (endothermic) = +

-= heat is released (exothermic)

Question 11

Which reaction is often favoured?

Answer 11

Exothermic reactions (release heat)

Question 12

What concept explains why sometimes endothermic reactions are favoured?

Answer 12

Entropy

Question 13

What is entropy and entropy change sign

Answer 13

Entropy (S) = the disorder of a substance

Entropy change triangle (S)

Question 14

What is the 2nd law of thermodynamics

Answer 14

Entropy S of a system either increases or remains the same (in terms of disorder you can’t go back to being ordered)

Question 15

How is solid to gas an example of entropy change

Answer 15

In a solid = ordered

Gas = disordered = most entropic

Question 16

Why is solid to gas enthalpically unflavoured but entropically favoured

Answer 16

Enthalpically unfavoured because it is endothermic (absorbs heat)

Entropically favoured because more disordered

Question 17

Do number of micro states increase when entropy /disorder increases?

Answer 17

Yes, in a gas there are multiple micro states (positions available)

Question 18

How does temperature relate to entropy

Answer 18

Kinetic energy if it drops, there are less micro states available (particles not in motion = no entropy)

Question 19

What is the 3rd law of thermodynamics

Answer 19

Entropy at 0 temperature = 0 itself

Question 20

How do you work out Gibbs free energy change?

Answer 20

Triangle G= enthalpy (H) change - (temp x entropy (S) change)

Question 21

If Gibbs free energy is negative a reaction takes place, why is this

Answer 21

Because if Gibbs free energy is negative , entropy is increased = entropically favoured (disorder)

Question 22

How do cells sometimes carry out unfavoured reactions?

Answer 22

They couple with favoured

Eg atp synthesis helped by H+ ion transport = favoured

Question 23

What determines the rate of reaction (collisions and reaction)

Answer 23

The kinetic energy available to overcome an activation energy barrier

Question 24

How is speed distributed to particles (kinetic energy)

Answer 24

Where they are put in a closed space and collide with eachother transferring energy to particles

Question 25

What 2 things affect the kinetic energy (speed of a particle)

Answer 25

1- temperature 2- mass (bigger = slower)

Question 26

How does temperature increase cause increase in rate of reaction

Answer 26

High temp = high kinetic energy Enough Ke can cause them to go over the barrier

Question 27

What is the first order reaction

Answer 27

A single molecule which dissociates into 2

Question 28

What is the second order reaction

Answer 28

Where 2 molecules will collide together to transfer kinetic energy

Question 29

What is the 3rd order reaction

Answer 29

3 molecules colliding together

Question 30

How would increasing concentration of molecules in first second and 3rd order increase rate of reaction

Answer 30

More likely collisions / dissociation

Question 31

How do you work out the equilibrium constant (Keq)

Answer 31

Conc of products (forward) / conc of reactants (backward)

Question 32

What does a positive Keq mean

Answer 32

More product than reactants in a beaker

Question 33

What does a negative Keq mean

Answer 33

More reactants than product in beaker

Question 34

At what point in a reaction is the change in Gibbs energy the lowest

Answer 34

At equilibrium

Question 35

What would adding reactant or product do to equilibrium

Answer 35

It would push Gibbs energy change from minimum The reaction counteracts it by either producing more reactant or product = equilibrium

Question 36

What is le chateliers principle

Answer 36

If something is pushed out of equilibrium eg by adding more reactant , it’s overcome by producing more product

Question 37

What is free energy

Answer 37

The useful energy left over when wasted work is lost

Question 38

What is chemical potential of solutes

Answer 38

The free energy of a solute at 1M | And accounting for entropy when mixing

Question 39

When is chemical potential of solutes the same?

Answer 39

At equilibrium

Question 40

What is the equilibrium potential

Answer 40

When the concentration gradient and an electrical gradient set up due to movement of ions are the same

Question 41

How does the Nernst equation find electrical gradient needed to for an equilibrium potential eg of K+

Answer 41

The Nernst potential is the voltage needed to oppose the conc gradient = reach potential equilibrium

Question 42

What actually allows for an electrical gradient

Answer 42

Movement of ions which causes negative or positive voltage within the cell and this attracts the ions back eg K+

Question 43

What would it be called if all of the ions involved were at their Nernst potential (potential equilibrium)

Answer 43

Donnan equilibrium

Question 44

Why is it unrealistic that all ions would be in equilibrium potential (ie no more net movement, conc equal in and out)

Answer 44

The cell would be hypertonic due to other macromolecules in it aswell as ions, The cell lives in a chemical disequilibrium due to the Na+ k+ pump = prevents cell bursting

Question 45

What 2 ways is free energy stored due to the increased H conc in the intermembrane of a mitochondria

Answer 45

1- chemical contributions (concentration gradient) 2- electrochemical gradient (the -160mv inside)

Question 46

What is the effect of the electrochemical gradient and the concentration gradient for free energy called in mitochondria which drives protons into ATPase

Answer 46

Proton motive force