
The normal boiling point of cyclohexane (enthalpy of vaporization: ) is . What will be its vapour pressure at ?
Answer
490.5k+ views
Hint: We can calculate the vapour pressure using the enthalpy of vapourization, temperature, and initial vapour pressure. We have to substitute the values of the enthalpy of vapourization, temperature, and initial vapour pressure in the expression below to get the vapour pressure at the given temperature.
Formula used: The formula to calculate the vapour pressure is,
Here represents the initial vapour pressure
represents the vapour pressure at the given temperature
represents the final temperature
represents the initial temperature
represents the enthalpy of vapourization
Complete answer:
The given data contains,
The value of is .
The value of is .
The value of is .
The value of is .
Let us now convert the degree Celsius into Kelvin by adding to the given temperature. The formula is written as,
Let us now substitute the given value of Celsius in the expression.
On adding we get,
The value of in Kelvin is .
The value of in Kelvin is .
Let us now use the expression to calculate the vapour pressure at the given temperature.
The formula to calculate the vapour pressure is,
Here represents the initial vapour pressure
represents the vapour pressure at the given temperature
represents the final temperature
represents the initial temperature
represents the enthalpy of vapourization
Let us now substitute the values of enthalpy of vapourization, temperatures, and pressure to get the vapour pressure at .
The vapour pressure at is calculated as,
On substituting the known values we get,
We get,
On simplification we get,
We have calculated the vapour pressure at is .
Note:
Based on the values and given variables we have to calculate the vapour pressure. We can also calculate the vapour pressure of the solution from mole fraction of the solvent and vapour pressure of the pure solvent. While calculating the vapour pressure from enthalpy of vapourization, we have to remember to convert the degree Celsius to Kelvin for temperatures failing which the exact vapour pressure could not be obtained.
Formula used: The formula to calculate the vapour pressure is,
Here
Complete answer:
The given data contains,
The value of
The value of
The value of
The value of
Let us now convert the degree Celsius into Kelvin by adding
Let us now substitute the given value of Celsius in the expression.
On adding we get,
The value of
The value of
Let us now use the expression to calculate the vapour pressure at the given temperature.
The formula to calculate the vapour pressure is,
Here
Let us now substitute the values of enthalpy of vapourization, temperatures, and pressure to get the vapour pressure at
The vapour pressure at
On substituting the known values we get,
We get,
On simplification we get,
We have calculated the vapour pressure at
Note:
Based on the values and given variables we have to calculate the vapour pressure. We can also calculate the vapour pressure of the solution from mole fraction of the solvent and vapour pressure of the pure solvent. While calculating the vapour pressure from enthalpy of vapourization, we have to remember to convert the degree Celsius to Kelvin for temperatures failing which the exact vapour pressure could not be obtained.
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