Question

a mercury barometer of 90 cm long contains some air above mercury,the reading is 74.5cm when true pressure is 76 cm hg at temperature 15 degree celcius ,another day the reading is 75.8 at temperature 5degree celcius then what will be it's true pressure?​

Answer 1

Answer:

Let the area of cross- section of the tube be A cm² and true pressure be H cm of mercury.

Since the temperature is constant, Boyle's law can be applied to the air enclosed in the upper part of the barometer tube, thus

According to Question,

P₁ = (76.0 - 74.5) = 1.5 cm of mercury

V₁ = A×(90 - 74.0) = A × 15.5cm³

P₂ = (H - 74.0) cm of mercury

V₂ = A × (90 - 74.0) = A × 16 cm³

Applying Boyle's law,

(Sorry, tried to solve the next step, but failed, this much I got)