W1 Thermochem

Question 1

1st law of thermodynamics in equations

Answer 1

ΔU = q + w

= ΔH - pΔV (at constant pressure)

q = heat of system = ΔH (at constant pressure)

w = work done on system = -pΔV (gases at constant pressure)

Question 2

Work done by gases equation

what does it mean if its negative/positive

Answer 2

w = pΔV

negative -> expansion

positive -> compression

Question 3

U

Answer 3

Internal energy

Sum of kinetic and potential energy of all particles in a system

U_total = U_kinetic + U_potential

Question 4

∆H

Answer 4

Function related to the heat absorbed or evolved by a chemical system - heat at constant volume (q_system= ∆H)

Question 5

Gibbs Free energy

Answer 5

Energy available to do work

∆G = ∆H - T∆S

Question 6

Standard enthalpy of reaction

Answer 6

Δ_rH^θ

value of ΔH for a reaction occuring under standard conditions (10⁵ Pa, 298K)

involves moles specified by question

Question 7

Enthalpy of formation

Answer 7

∆_fH^ɵ

energy required to form one mol of a substance from its elemental parts under standard conditions (10⁵ Pa, 298K)

Question 8

Entropy of surroundings equation

Answer 8

∆S_surroundings = q_surroundings/T

Question 9

2nd law of thermodynamics

Answer 9

For a spontaneous reaction: ΔS_total > 0

Question 10

Definition of entropy

Answer 10

S = k lnW

K is Botlzmann’s constant, W is the number of microstates that the energy of a system can be distributed

Question 11

Factors that affect entropy

Answer 11

Higher entropy caused by:

• Higher volume
• Higher temperature
• State: Gas > water > solid
• Higher no. particles

Question 12

Gibbs free energy related to K

Answer 12

Under equilibrium conditions, ∆_rG is zero so: ∆G^θ= - R T InK