Question

How did you calculate boiling point at different pressures?

Answer 1

The variation of boiling point at different pressures is determined by Clausius-Clapeyron Equation. This equation is given as;
$\ln \dfrac{{{P}_{2}}}{{{P}_{1}}}=\dfrac{-\Delta {{H}_{vap}}}{R}\left( \dfrac{1}{{{T}_{2}}}-\dfrac{1}{{{T}_{1}}} \right)$
where,
$\Delta {{H}_{vap}}$ = enthalpy of evaporation
R = gas constant
P = pressure
T = temperature

Complete answer:
To calculate the boiling point at different pressures, we have some steps;
Step I-
Identify the known and unknown variables given in the statement.
Step II-
Identify the formula to be used to solve and calculate the unknown terms from the known ones.
Step III-
Put the known variables into the proper formula.
Step IV-
Finally solve every other formula to reach the final stage and calculate the boiling point.
Step V-
Solve the same sequence when the known parameters change. Repeat the steps.
Therefore, using these common steps we can find out the variation in boiling point with respect to different pressures.

Note:
Do note that there are other methods to determine boiling points with varying pressure along with Clausius-Clapeyron equation. They are estimation at higher altitudes, using Nomographs, using on-line calculators, etc.