Question

A glass contains some water at room temperature 20°C. Refrigerated water is added to it slowly. when the temperature of the glass reaches 10°C, small droplets condense on the outer surface. Calculate the relative humidity in the room. The boiling point of water at a pressure of 17.5 mm of mercury is 20°C and at 8.9 mm of mercury it is 10°C.

Answer 1

$\begin{array}{l}\text{Here,}\\ \\ {\text{Dew point = 10}}^{0}C\left[{\text{∵ Dew appears at 10}}^0\mathrm{C}\right]\\ \text{At boiling point, SVP equals atmospheric pressure}\text{.}\\ {\text{At 20}}^{0}C,\text{SVP = 17}\text{.5 mmHg}\\ \text{At dew point},SVP\text{= 8}\text{.9 mmHg}\\ \text{RH=}\frac{\text{SVP at dew point}}{\text{SVP at air temperature}}\times 100\%\\ =\frac{8.9}{17.5}\times 100\%\\ =51\%\end{array}$