Physical Chemistry Answers

The density of 2M CH,COOH solution is 1.2 g/mL.Find other concentration terms (molality, X solute%w/w and %w/v).

Given the following data:
( ) ( ) ( ) ( ) 2 2 2 CO g H O g CO g H g + à ƒ ¢ † ’ + H ( C)
o o à ƒ ¯  „ 25
= -42.0 kJmol-1
Cp (CO) = 26.8 + 6 x 10-3T JK-1mol-1
Cp (H2O) = 30.1 + 10 x 10-3T JK-1mol-1
Cp (H2) = 28.5 + 2 x 10-3T JK-1mol-1
Cp (CO2) = 26.4 + 42 x 10-3T JK-1mol-1
where T is the thermodynamic temperature, calculate the change in enthalpy for the
reaction at 1000 K.

Calculate the heat of formation of HCl at 348 K from the following data
2 2 ( ) ( ) ( )
1 1 H g Cl g HCl g
2 2
+ à ƒ ¢ † ’
;
o à ƒ ¯  „H298K
= - 92.3 kJ
The mean heat capacities in the temperature range 298 K and 360 K are:
H2(g): Cp = 28.53 JK-1mol-1
Cl2(g): Cp = 32.26 JK-1mol-1
HCl(g): Cp = 28.49 JK-1mol-1

The enthalpy changes of CO2(g) and H2O(l) under standard conditions are 394.65 kJ/mol and
285.84 kJ/mol, respectively. If the enthalpy change of combustion of acetaldehyde (CH3CHO)
is 1167.62 kJ/mol, find its standard enthalpy change of formation,
o à ƒ ¯  „Hf
.

Calculate the enthalpy of formation of carbon disulphide given the following thermochemical
equations of combustion of CS2(s), C(s) and S(s):
CS2(s) + 3O2(g)
à ƒ ¢ † ’
CO2(g) + 2SO2(g) à ƒ ¢ ˆ †H
o = - 1109 kJ
C(s) + O2(g)
à ƒ ¢ † ’
CO2(g) à ƒ ¢ ˆ †H
o = - 394.6 kJ
S(s) + O2(g)
à ƒ ¢ † ’
SO2(g) à ƒ ¢ ˆ †H
o = - 298.7 kJ

Compare the thermodynamic efficiencies to be expected:
(a) When an engine is allowed to operate between 1000 K and 300 K.
(b) When an engine is allowed to operate between 1000 K and 600 K and then waste heat
passed on to another engine which operates between 600 K and 300 K.

Consider the reaction A(g) + B(g)
à ƒ ¢ † ’
2C(g). For this reaction, à ƒ Ž ”Ho = -116 kJ mol-1 and the
equilibrium constant Kp is 140 at 600 K. Calculate for this reaction (i) à ƒ Ž ”Go and (ii) à ƒ Ž ”So at 600 K.

The normal boiling point of water is 100
oC. Its vapour pressure at 80oC is 0.4672 atm. Calculate
the enthalpy of vaporisation per mole of water, given that R is 8.314 JK-1mol-1
.

The equilibrium constant of a hypothetical reaction
AB(g) A(g) + B(g)
was determined as a function of temperature and the data was fitted using the linear form of
the vanà ƒ ƒ ¢ € ™t Hoff isochore and the result was:
p
15000 ln K 24.85
T
= +
Use these results to obtain à ƒ ƒ Ž ”H
o
, à ƒ ƒ Ž ”S
o and à ƒ ƒ Ž ”G
o at 298 K.

The vapor pressures of solid and liquid chlorine in the vicinity of the triple point are given by
( )
3755 ln P /Pa 26.88 solid T
= à ƒ ƒ ƒ ¢ ˆ ’
and
T
2661 / Pa 22.76 liquid ln P à ƒ ƒ ƒ ¯ ƒ · = à ƒ ƒ ƒ ¢ ˆ ’
à ƒ ƒ ƒ ¯ ƒ ¸
à ƒ ƒ ƒ ¯ ƒ ¶
à ƒ ƒ ƒ ¯ ƒ §
à ƒ ƒ ƒ ¯ ƒ ¨
à ƒ ƒ ƒ ¯ ƒ ¦
Determine the triple point pressure and temperature, and à ƒ ƒ ƒ ¢ ˆ †Hfusion and à ƒ ƒ ƒ ¢ ˆ †Sfusion at triple point.