Chemistry - Ideal Gas Question with Solution | TestHub
A 2 m long tube closed at one end is lowered vertically into water until the closed end is flush with the water surface. Calculate the water level height h in the tube (see figure: h = distance of inside water level below the closed end). (Barometric pressure = 1 atm = 10 m of hydrostatic water head. Temperature = 25°C, Density of water 1.00 g/ml. Neglect water vapour pressure)
Options:
Answer:
Solution:
Let a = distance of the inside water level below the closed end, i.e. the trapped air column length. The trapped air is at pressure (10 + a) m of water head, since the inside level lies a m below the surface. Boyle's law: 10 × 2 = (10 + a) a ⇒ a2 + 10a - 20 = 0 ⇒ a = (-10 + √(180))/2 = 1.71 m. So the water level stands h = 1.71 m below the closed end (the water column itself rises only 2 - 1.71 = 0.29 m). Matches (c).
