When a student plotted ln [vapor pressure of a gas] vs. inverse Kelvin temperature, she obtained a straight line with a slope equal to -20000 K.
According to the Clausius Clapeyron equation, change in Hvap is _____ kJ/mol.
This tells you what to do.
http://www.science.uwaterloo.ca/~cchieh/cact/c123/clausius.html
I cannot get to the website. Can you show me how to approach this problem?
To find the change in Hvap (enthalpy of vaporization) using the Clausius Clapeyron equation, we need to know the slope of the ln (vapor pressure) vs. 1/T graph. Since the slope is given as -20000 K, we can use this information to calculate the enthalpy change.
The Clausius Clapeyron equation relates the change in vapor pressure (ΔP) to the change in enthalpy (ΔHvap) and the temperature (T) using the equation:
ln (P2/P1) = -ΔHvap / R * (1/T2 - 1/T1)
In this equation, ln (P2/P1) represents the natural logarithm of the ratio of vapor pressures at two different temperatures (usually expressed as P2/P1). R is the ideal gas constant (8.314 J/(mol K)).
From the given information, we have the slope (-20000 K). The slope of a linear equation represents ΔHvap / R. Therefore, we can rewrite the given slope as:
-20000 K = ΔHvap / R
Now, substituting the value of R into the equation, we get:
-20000 K = ΔHvap / 8.314 J/(mol K)
To find the value of ΔHvap, we can rearrange the equation:
ΔHvap = -20000 K * 8.314 J/(mol K)
Calculating this expression will give us the enthalpy change in joules per mole (J/mol). If you want the answer in kilojoules per mole (kJ/mol), you can convert it by dividing the obtained value by 1000.
Please note that without the exact value of the slope and the units used, the final answer may vary.