Question

At what external pressure will water boil ${140}^{\circ }C$? (S VP at ${140}^{\circ }C$ =2710 mmHg)

• A. 2.53
• B. 3.56
• C. 1
• D. None

Answer 1

The correct option is B 3.56

The saturation vapour pressure of water at ${140}^{\circ }C$ is 2710 mm of Hg, Thus. Water will boil at ${140}^{\circ }C$ at this pressure. Now 760 mm of Hg = 1 atm.
Thus, 2710 mm of $Hg=\frac{2710}{760}$ atm = 3.56 atm
The pressure inside a pressure cooker is of this order when it whistles. So, the temperature inside is of the order of ${140}^{\circ }C$ which helps in cooking the food much faster.