A faulty barometer has some trapped air above the mercury column due to which it does not give the correct reading. When the atmospheric pressure is 770 mm Hg, the barometer reads 760 mm Hg and when t

Question

A faulty barometer has some trapped air above the mercury column due to which it does not give the correct reading. When the atmospheric pressure is 770 mm Hg, the barometer reads 760 mm Hg and when the pressure is 810 mm Hg, the barometer reads 780 mm Hg. The actual pressure (in mm Hg), when the barometer reads 770 mm Hg, is

TestHub · Accepted Answer

Trapped air: state 1 at 770 - 760 = 10 mm Hg in length (L - 760); state 2 at 810 - 780 = 30 mm Hg in (L - 780).

Boyle: 10(L - 760) = 30(L - 780) ⇒ L - 760 = 3L - 2340 ⇒ L = 790 mm.

Trapped-air constant = 10 × (790 - 760) = 300. At reading 770: p = 300/(790 - 770) = 15 mm Hg.

Actual pressure = 770 + 15 = 785 mm Hg ⇒ 0785.

Chemistry - Ideal Gas Question with Solution | TestHub

Doubts & Discussion