Chemistry - Ideal Gas Question with Solution | TestHub
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 760 mm Hg, the barometer reads 750 mm Hg and when the pressure is 800 mm Hg, the barometer reads 770 mm Hg. The actual pressure (in mm Hg), when the barometer reads 760 mm Hg, is
Answer:
Solution:
Let L be the length of the barometer tube above the reservoir level. The trapped air occupies (L - h) when the column reads h, at pressure (Patm - h).
State 1: trapped air 10 mm Hg × (L - 750). State 2: 30 mm Hg × (L - 770).
Boyle: 10(L - 750) = 30(L - 770) ⇒ L - 750 = 3L - 2310 ⇒ 2L = 1560 ⇒ L = 780 mm.
Trapped-air constant = 10 × (780 - 750) = 300 mm2 Hg... i.e. p × (780 - h) = 300.
At reading 760: p = 300/(780 - 760) = 15 mm Hg.
Actual pressure = 760 + 15 = 775 mm Hg ⇒ 0775.
