Question

In butane properties is that at 20 C & it's vapour pressure (absolute pressure) 220 kPa similarly, at 40 C is 360 kPa, at 45C is 385 kPa & 55C is 580 kPa. How they calculate these pressure on given temp

Answer 1

Answer on Question #57282 – Chemistry – General chemistry

Question

In butane properties is that at 20 C & it's vapour pressure (absolute pressure) 220 kPa similarly, at 40 C is 360 kPa, at 45C is 385 kPa & 55C is 580 kPa. How they calculate these pressure on given temp

Answer

We may calculate these pressure on given temp from the Clausius-Clapeyron equation.

$$\ln \frac {P 1}{P 2} = \frac {\Delta H v a p}{R} \left(\frac {1}{T 2} - \frac {1}{T 1}\right)$$ $$\ln (P 1 / P 2) = (\Delta H _ {v a p} / R) ((1 / T 2) - (1 / T 1))$$

Where:

P1 – vapor pressure at the temperature T1

P2 – vapor pressure at the temperature T2

$\Delta H_{\mathrm{vap}}$ – cas constant

T1 is temperature at which the vapor pressure is known

T2 is temperature at which the vapor pressure is to be found.

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