Calculate the temperature at which water has a vapour pressure of 19 mm Hg.

Here are the solutions to the problems:

: Vapour pressure and temperature

Step 1: Identify the given values and the formula to use.
We are given:

• Normal boiling point of water $T_1 = 373$ K (at $P_1 = 1$ atm $= 760$ mm Hg)
• Enthalpy of vaporisation $\Delta H_{vap} = 40.67$ kJ/mol $= 40670$ J/mol
• Target vapour pressure $P_2 = 19$ mm Hg
• Gas constant $R = 8.3$ J K$^{-1}$ mol$^{-1}$
• We need to