Question

The vapor pressure of water at 21.0 oC is 18.650 torr and the vapor pressure of water at 21.2 oC is 18.880 torr. How can you find vapor pressure of water at 21.1 oC? Explain your reasoning and give your determination of the vapor pressure of water at 21.1 oC.

Answer 1

The pressure at 21.1°C is 18765torr.

Why?

Since we know the pressures at 21.0°C and 21.2°, if we want to find the pressure at 21.1°C, wee need to use the formula for linear interpolation.

We will need to use the following formula to linear interpolation:

$y=\frac{x-x_{1}}{x_{2}-x_{1}}*(y_{2}-y_{1})+y_{1}$

Then, we have:

$21.0\°C=18650torr\\21.2\°C=18880torr\\21.1\°C=???\\\\x_{1}=21.0\°C,y_{1}=18650torr\°C\\\\x_{2}=21.2\°C,y_{2}=18880torr\\\\x=21.1\°C,y=???$

So, interpolating we have:

$y=\frac{(21.1\°C-21.0\°C)}{(21.2\°C-21.0\°C)}*(18880torr-18650torr)+18650torr\\\\y=115torr+18650torr=18765torr$

Hence, the pressure at 21.1°C is 18765torr.

Have a nice day!