2 quick chemistry/physics questions? Please Help!! Thanx! =D?

Question

1) A 500 mL sample of helium gas contains 2.0 moles of gas at 300 K.
(a) Find the pressure exerted by the particles.
(b) If the temperature is doubled and half of the gas escapes, what will be the new pressure?

2) Oxygen gas is released from a cylinder at the rate of 10 m^3 per hour at atmospheric pressure. If it is sold at a pressure of 200 atm and has a volume of 2.0 m^3, for how long will it supply oxygen?

Please help me do these 2 questions (and explain the steps) because I’m really having trouble with these 2. THANX to everyone who can help!! =D

Answer 1

1)
a) pV=nRT p= nRT/V
you put all iN MKSA
so V= 5*10^-4m^3 , n=2 R=8.314
p= 2*8.314*300/5*10^-4=9.98*10^6 Pa=98.1atm
b)if temperature is doubled,the pressure should be doubled but if half the gaz escapes n is divided by 2. So, with both effects 2*1/2=1, no change (same answer as a)

2) the mass of oxygene SOLID does not depend on the temperature. But to make your problem you must give me the density of solid oxygen. suppose it is d grams/cm3
its mass will be 2*d*10^6g for your problem and corresponds to a number of moles 2/32*d*10^6=62500moles. at 300K this corresponds to 62500*25l =1562m^3 So you must wait
156.2 hours

Answer 2

Since someone answered qn1)

2)
Rate = (200 atm x 2.0 m^3) / (1 atm x 10 m^3/hr)

This should give you the answer in hours.

Answer 3

1)For ideal gas we have: PV=NRT
Data: P=? , V=500ml=0.0005m^3 , N=2mol , R=8.314, T=300k
(a) P=9976 kPa
(b) V=250ml=0.00025m^3 ,T=600k then P=39907 kPa

2) sorry,I don't know this one.

Answer 4

i guess the guy above me already answered your question