Thermodynamics

Question 1

Ideal gas law

Answer 1

pV=nRT

Question 2

ideal gas law units

p

v

n

r

t

Answer 2

P= Nm-2

V= m3

n= mol

R = 8.314 J K-1 mol-1

T= K (+273)

Question 3

when does the ideal gas law work

Answer 3

WORKS WELL FOR GASES AT HIGH TEMPERATURE

Question 4

m³ to dm³

Answer 4

1 m³ = 1000 dm³

Question 5

partial pressures

Answer 5

Question 6

Why is the ideal gas law not accurate

Answer 6

1) neglects molecular interaction
2) neglects the volume of molecules

Question 7

Compressiong factor

Answer 7

The compressibility factor (Z) is a correction factor which describes the deviation of a real gas from ideal gas behaviour. It is simply defined as the ratio of the molar volume of a gas to the molar volume of an ideal gas at the same temperature and pressure. It is a useful thermodynamic property for modifying the ideal gas law to account for the real gas behaviour.

Question 8

When is the deviaion from ideal gas law is significant

Answer 8

In general, deviation from ideal behaviour becomes more significant the closer a gas is to a phase change, the lower the temperature or the larger the pressure.

Question 9

Compression factor eqn

Answer 9

Question 10

Real gas law and units

Answer 10

a and b change as molecular size increases

Question 11

Internal energy U

Answer 11

Question 12

definition and formula of enthalpy

Answer 12

H = U + pV
The enthalpy of a substance is a measure of the total

energy of a thermodynamic system.

It includes the internal energy (sum of kinetic and potential energies), plus an additional term, pV (which is the energy required to “make room for it” by displacing its surroudings).

Energy transferred as heat at constant pressure = enthalpy change H

Question 13

energy conservation

Answer 13

In chemical changes, energy can be converted from one form to another but not destroyed
=> i.e. energy conservation

Question 14

Changes to the internal energy of a system

Answer 14

1) heat transfer (q) to and from surroundings (enthaly change)
2) work done (w) (on or by system)

Question 15

changes in internal energy formula

Answer 15

Question 16

Effect of heat transfer on internal energy

1) surrounding –> system
2) system –> surrounding

Answer 16

1) surrounding –> system q= +ve /_\ U increase
2) system –> surrounding q= -ve /_\ U decrease

Question 17

work formula

Answer 17

Question 18

/_\ U formula

Answer 18

Question 19

Use of differntials in chemistry

Answer 19

check notes pg 14

Question 20

ideal gas and the First Law Constant volume change (isochoric)

Answer 20

dV = 0
dw = -pdV = 0

/_\U = q

Question 21

ideal gas and the First Law Constant pressure change (isobaric)

Answer 21

dw = -pdV w = - ∆ pdV

w =-p ∆dV = -p ∆V (as p is constant)

∆U= q-p∆V ∆U =∆H - p ∆V

Question 22

ideal gas and first law No heat change (adiabatic)

Answer 22

q =0

∆U = w

Question 23

ideal gas and first law Constant temperature change (isothermal)

Answer 23

∆U = 0

q = -w

Question 24

Heat capcity

Answer 24

Question 25

Heat capacity at constant V

Answer 25

Question 26

Heat capacity at constant P

Answer 26

Question 27

ideal gas of atoms

Answer 27

Question 28

Calorimeter

Answer 28

used to measure /_\ T for a reaction (and hence measure heat changes)

Question 29

Cv at constant volume

Answer 29

Question 30

Cp at constant pressure

Answer 30

Question 31

Bomb calorimeter

Answer 31