Chemical Thermodynamics

Question 1

Define Internal Energy

Answer 1

The sum of potential and kinetic energies of a system

Question 2

What are Heat and Work Examples of ?

Answer 2

Energy Transfer

Question 3

Define Heat Transfer

Answer 3

Flow of energy between two systems in thermal contact with different temperatures

Question 4

Define Work

Answer 4

Transfer of an energy using a force

Question 5

What are the dimensions of a Joule

Answer 5

kg M^2 s^-2

Question 6

What is Change in Internal Energy

Answer 6

Transfer of energy from heat + transfer of energy from work

q+w

Question 7

What is Specific heat Capacity?

Answer 7

Heat required to raise the temperature of a gram of material by 1 kelvin .

Question 8

Calculate the energy required to brew a single cup of tea, 350ml of tap water 283K , is brought to 371K.

Water = 1gcm^-3

cp(water) = 75.2J

Answer 8

Question 9

What is the Equation for Change in Enthalpy at constant pressure

Answer 9

Delta Enthalpy = Delta Internal Energy + pressure * Change in volume

Delta H = Delta U + P Delta V

Question 10

What is Enthalpy

Answer 10

Heat flow of a system at constant pressure

Question 11

Derive that Enthalpy is equal to heat flow of a system at constant pressure

Answer 11

Delta H = Delta U + P Delta V

Delta H = q + w + P Delta V

P Delta V = work done by the system against the surroundings

w = work done by surroundings on the system

Hence Delta H = q

Question 12

At constant volume what is the Enthalpy?

Answer 12

at constant volume the container the gas cannot thermally expand

Hence work done on the system by the gas is zero.

so Delta H = Delta U = q

Question 13

Answer 13

Question 14

What is Enthalpy of Formation

Exo or Endo?

Answer 14

The enthalpy change when 1 mol of a compound is formed from its element in their standard states under standard conditions

2Na(s) +O2(g) -> Na2O(s)
Exothermic

Question 15

What is Enthalpy of combustion

Exo or Endo?

Answer 15

The Enthalpy change when 1 mol of a substance is completely burnt in oxygen under standard conditions with all reactants and products are within their standard state.

H2(g) + O2(g) -> H2O(g)
Exothermic

Question 16

What is the Equation for heat transfer at constant pressure?

Answer 16

q = M C Delta T

q = n C(p) Delta T

Where M = mass , C(p) = Pressure Heat capacity, n = number of moles. Delta T = Change in Temperature

Question 17

What are Isothermal changes to a system?

Answer 17

Changes at Constant Temperature

Question 18

What are Adiabatic Changes to a system?

Answer 18

Changes with no energy transfer via heat across the system boundary

Question 19

How do you calculate Entropy , using the number of microstates and the Boltzmann constant

Answer 19

S = K(b) ln(Microstates)

Question 20

what are microstates

Answer 20

collection of particles assuming the same energy.

Question 21

In a spontaneous reaction, entropy can __________________________________.

Answer 21

Either increase or remain the same.

Question 22

Write and equation that explains the second law of thermodynamics

Answer 22

Question 23

Change in entropy of surroundings =

Answer 23

-1 * Delta H / T

opposite to system

Question 24

What is the equation for Change in Gibbs Free Energy

Answer 24

G = H - TS

Delta Gibbs = Delta Enthalpy - Temperature * Delta Entropy

Question 25

What is important to remember in free gibs calculations

Answer 25

T is in Kelvin

Question 26

Answer 26

in hess cycle , arrows go from below upwards

Question 27

Answer 27

Question 28

fill the table in

Answer 28