Question

8]] a) the number of moles of O2 in 56.4 L of O2 gas

b) the volume, in liters, occupied by 0.170 mole of He gas

1.24 If the partial pressures are oxygen 440 torr and helium 40 torr , what is the partial pressure (torr) of the nitrogen in the mixture?

1.25 . If the partial pressure of oxygen drops below 110 mmHg , passengers become drowsy. If this happens, oxygen masks are released. What is the total cabin pressure at which oxygen masks are dropped?

Answer 1

Since there is no information about Temperature and Pressure, it is assumed that O2 and He are at STP.

At STP, P = 1 atm , T = 273 K

8) a) It is assumed that O2 gas is at STP

At STP,

P = 1 atm

T = 273 K

Given that Volume of O2 gas V = 56.4 L

number of moles of O2 gas , n = ?

Ideal gas equation is

PV = nRT R = universal gas constant = 0.0821 L.atm/K/mol

n = PV/RT

= 1 atm x 56.4 L / ( 0.0821 L.atm/K/mol x 273 K)

= 2.52 moles

Therefore,

number of moles of O2 in 56.4 L of O2 gas = 2.52 moles

b)

It is assumed that He gas is at STP.

At STP,

P = 1 atm

T = 273 K

Given that number of moles of He gas, n = 0.17 moles

volume of He gas, V = ?

Ideal gas equation is

PV = nRT R = universal gas constant = 0.0821 L.atm/K/mol

V = nRT/P

= 0.17 moles x 0.0821 L.atm/K/mol x 273 K / 1 atm

= 3.81 L

Therefore,

volume occupied by 0.170 mole of He gas = 3.81 L