Question

Liquid sodium can be used as a heat transfer fluid. Its vapor pressure is 40.0 torr at 633°C and 400.0 torr at 823°C. Calculate its heat of vaporization.

Answer 1

Answer:

H vaporization = 100.0788 kJ/mol

Explanation:

Use clausius clapyron's adaptation for the calculation of Hvap as:

$ln\frac {P_2}{P_1}=\frac {H_{vap}}{R}(\frac {1}{T_1}-\frac {1}{T_2})$

Where,

P₂ and P₁ are the pressure at Temperature T₂ and T₁ respectively.

R is the gas constant.

T₂ = 823°C

T₁ = 633°C

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15  

So, the temperature,

T₂ = (823 + 273.15) K = 1096.15 K

T₁ = (633 + 273.15) K = 906.15 K

P₂ = 400.0 torr , P₁ = 40.0 torr

R = 8.314 J/K.mol

Applying in the formula to calculate heat of vaporization as:

$ln \frac {400}{40}=\frac {H_{vap}}{R} (\frac {1}{906.15}-\frac {1}{1096.15})$

Solving for heat of vaporization, we get:

H vaporization = 100078.823 J/mol

Also, 1 J = 10⁻³ kJ

So,

H vaporization = 100.0788 kJ/mol