# Gas Laws

#### uniidiot

1. Homework Statement
A 200g sample of CO2 occupies a volume of 110 L at a pressure of 1 atm.

a) What is the number of moles in the gas

b) What is the temperature?

c) if the volume is increased up to 200 L and the temperature is kept constant. what is the new pressure.

2. Homework Equations

3. The Attempt at a Solution
a) 110/24.7 = 4.45 ( i think thats right)

b) pV = constant is that constant the temperature???

if so the temperature = 1 x 110 = 110

c) ( p1 v1 ) / T1 = ( p2 V2 ) / T2

(1 x 110) / 110 = ( p2 x 200) / 110

p2 = (1 x 110 x 110) / (110 x 200) = 0.55

i'm not sure if i'm doing this right can anyone help?

THANKS!

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#### G01

Homework Helper
Gold Member
For part a)

I'm sorry, but I don't understand what you're doing here. HINT: How many grams in one mole of CO2?

For Part b)

I think you're thinking of the Ideal Gas Law. If so, that is:

$$PV=nRT=NkT$$

where n=number of moles, R=gas constant, N=number of molecules, k=Boltzman's constant.

If you can do the above, then you should get part c) right, since your method above was correct.

Good Luck!

Last edited:

#### Chi Meson

Homework Helper
A) how about a few units? What is "24.7" here?

b) no, not at all.

c) 0.55 whats? ATM here, despite having the wrong temperature.

EDIT: BLAST! beaten again by GO1 !

#### G01

Homework Helper
Gold Member
EDIT: BLAST! beaten again by GO1 !
Heh! Sorry Chi, I'm just quick and sneaky like that!

#### uniidiot

ok well the ratio of CO2 is

12:32

one mole of C is 6.02x10^23 x 12

one mole of O is 6.03x10^23 x 16

but how do i work out how much of the 200g is carbon?

thanks so far!

#### uniidiot

ok scrap that last post lol,

1 mole of carbon-12 is 12 grams,
1 mole of oxgen-16 is 16 grams,

so i still need to know how much of the 200g is carbon.

thanks

#### Dick

Homework Helper
CO2 is a molecule consisting of one atom of carbon and two of oxygen. So one mole of CO2 is one mole of C plus two moles of O.

#### uniidiot

CO2 is a molecule consisting of one atom of carbon and two of oxygen. So one mole of CO2 is one mole of C plus two moles of O.
oh ok, so does that mean that the number of moles in 200g of CO2 is

0.2 (kg) / (6.02 x 10^32)

all x 3 becuase there are 3 moles per molecule

#### nrqed

Homework Helper
Gold Member
oh ok, so does that mean that the number of moles in 200g of CO2 is

0.2 (kg) / (6.02 x 10^32)

all x 3 becuase there are 3 moles per molecule
What is the mass of one mole of CO2? (you already gave the mass of one mole of C and of O so that will be easy.

Once you have the mass of one mole of CO2, you simply have

number of moles of CO2 = 200 gr/(mass per mole of CO2)

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