enthalpy

Question 1

work definition

Answer 1

transfer of energy to ordered motion

Question 2

heat definition

Answer 2

chaotic transfer of energy

Question 3

internal energy definition

Answer 3

the sum of all kinetic and potential energy of a species

Question 4

relationship between Cp and Cv

Answer 4

Cp = Cv + R

Question 5

Equipartition theory values

Answer 5

translation = 1.5R
rotation = 1.5/1 R
vibration = R mol-1

Question 6

What is the sum of the equipartition values

Answer 6

heat capacity per mole

Question 7

enthalpy change with volume definition

Answer 7

dH = dU + pdV OR
dH = dU + dnRT

Question 8

when is enthalpy change and its relation to pressure relevant

Answer 8

For gases, for liquids and solids there is little change in volume with changes in enthalpy

Question 9

what is enthalpy change at constant pressure

Answer 9

q (heat)

Question 10

isothermal conditions

Answer 10

systems can exchange heat with their surroundings (constant temperature)

Question 11

isothermal work equation

Answer 11

w = p*dV

Question 12

instantaneous isothermal expansion

Answer 12

instantaneous inherently means that pressure is constant
w = -pdV

Question 13

work done by infinitely slow (reversible)
isothermal expansion

Answer 13

w = - RTln(Vf/Vi)

Question 14

dU for a perfect gas

Answer 14

dU = q + w (balance between work done and heat exchanged)

Question 15

adiabatic conditions

Answer 15

cannot exchange heat with their surroundings

Question 16

what is lamda

Answer 16

Cp/Cv

Question 17

what is pressure proportional to under adiabatic conditions

Answer 17

1/V^lamda

Question 18

c definition

Answer 18

Cv,m/R (molar Cv/R)

Question 19

Temperature change under adiabatic conditions

Answer 19

Tf = Ti(Vi/Vf)^1/c

Question 20

Finding enthalpy given Cp and T under adiabatic conditions

Answer 20

The area under a plot of Cp against T

Question 21

Final enthalpy under adiabatic conditions

Answer 21

H2 = H1 + integral(Cp(T))

Question 22

The Kirchhoff equation

Answer 22

(dH/dT) = dCp

Question 23

Calculating Cv from a calorimeter

Answer 23

E = IVt
IV = W and I is the current and V is the voltage
t is time in s

then E = qv = CvdT

Question 24

Converting internal energy to enthalpy of a gas

Answer 24

dH = dU + dnRT
where dn is the change in the number of moles of a gas during chemical reaction

Question 25

Internal energy from a calorimeter

Answer 25

dU = CvdT

Question 26

pressure and volume after irreversible isothermal or adiabatic expansion

Answer 26

isothermal : p1V1 = p2V2
adiabatic: p1V1^lamda = p2V2^lamda