Question

Calculate the atmospheric pressure if the boiling point of water is 81 degrees Celsius.

Answer 1

To calculate the atmospheric pressure at a specific boiling point of water, we use the steam table or the Antoine equation. From steam table via interpolation, at 81 C, the pressure where saturation occurs is the atmospheric pressure. The atmospheric pressure is 369.7 mm Hg or 0.4864 atm.

Answer 2

Answer : The atmospheric pressure of water if boiling at 81 °C will be 369 mmHg.

Explanation : The vapor pressure of boiling water can be calculated using the Antoine Equation:

log P = A - $[\frac{B}{ C + T} ]$,

where P is the pressure in mmHg,

A = 8.07131,

B = 1730.63

C = 233.426

and T = temperature in °C (81°C)

Substituting the given values, we get,

Log P = 8.07131− $[\frac{1730.63}{233.426 + 81}]$

Therefore, Log P =8.07131 − 5.5041 = 2.567.

Now, P = $(10^{2.567} )$ =369 mmHg.

Hence, the atmospheric pressure will be 369 mmHg.