Question

A mouse is placed in a sealed chamber with air at 768.0 torr. This chamber is equipped with enough solid KOH to absorb any CO₂ and H₂O produced by the mouse. The gas volume in this chamber is measured to be exactly 1.90 L, and the temperature is held constant at 309K. After two hours the pressure inside the chamber falls to 725.2 torr. What mass of oxygen has the mouse consumed?

Answer 1

Pair = 768 torr

V1 = 1.90 L

T = 309K

after t = 2 h, the P is 725.2 torr

find mass of O2(g)

Apply

PV = nRT

where

P = absolute pressure

V = total volume of gas

n = moles of gas

T = absolute Temperature

R = ideal gas constant

n = PV/(RT) = (768*1.90)/(62.4*309)

n = 0.075678 moles initially of AIR

P1V1/(n1*T1) = P2V2/(n2*T2)

T1 = T2, V1 = V2 so

P1/n1= P2/n2

768/n1 = 725.2/n2

n2 = 725.2/768*0.075678

n2 = 0.071460 moles of AIR

since 21% is O2 from air:

mol of O2 = 0.21*0.071460 = 0.0150 mol is oxgyen

mass = mol*MW = 0.01500*32 = 0.48 g of O2