Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: jylxox on October 23, 2009, 08:55:07 PM

Title: Calculating density using temp. and pressure
Post by: jylxox on October 23, 2009, 08:55:07 PM

Calculate the density, g/cm3, of carbon dioxide   at   98.0 oC   and   807 torr.

Title: Re: Calculating density using temp. and pressure
Post by: Boosted55 on October 23, 2009, 09:06:30 PM

First you need the formula to find density, which is d = PM / RT.
Convert 807 torrs to atm by dividing by 760 torr. 807 torr x (1 atm / 760 torr) = 1.06 atm
Then find the molar mass of carbon dioxide, which is ~44g.
R is a constant. (~0.0821)
Convert 98.0 degree C to K, with is 98 + 273.15 K.
The plug everything in and you are good to do. Also remember that mL=cm3.

Title: Re: Calculating density using temp. and pressure
Post by: jylxox on October 24, 2009, 12:57:42 PM

That's what I did.
P= 1.06 atm
M = 44 g
R = .0821
T= 371

(1.06 times 44)/(.0821 times 371) = 1.53

And the system says that the answer is wrong.

Title: Re: Calculating density using temp. and pressure
Post by: Borek on October 24, 2009, 04:06:09 PM

What units is your answer in?

Title: Re: Calculating density using temp. and pressure
Post by: jylxox on October 24, 2009, 05:43:30 PM

The units are supposed to be g/cm cubed.

The units are not included in the answer.

Title: Re: Calculating density using temp. and pressure
Post by: Borek on October 24, 2009, 06:46:51 PM

I am not asking what they are supposed to be, but what they ARE. You have calculated density to be 1.53 - of what? Pounds per kilogalon? Stones per cubic meter? Ounces per pint?

Title: Re: Calculating density using temp. and pressure
Post by: jylxox on October 25, 2009, 02:55:49 PM

P= 1.06 atm
M = 44 g./mol
R = .0821
T= 371 K

(1.06atm times 44g/mol)/(.0821 times 371K) = 1.53g/cm cubed.

Title: Re: Calculating density using temp. and pressure
Post by: Borek on October 25, 2009, 03:49:04 PM

No. Check your units, especially for R.

Title: Re: Calculating density using temp. and pressure
Post by: butterwings on October 26, 2009, 10:24:05 AM

the R is equal to 0.08206, but it still the similar answer.

i dont understand this problem too! someone plz help?!

Title: Re: Calculating density using temp. and pressure
Post by: Borek on October 26, 2009, 10:59:15 AM

I am not asking about numerical value, I am asking about UNITS.

For example - molar mass has units [gram/mole]. What units is ideal gas constant in, when its value is 0.0821?

Title: Re: Calculating density using temp. and pressure
Post by: typhoon2028 on October 26, 2009, 11:26:27 AM

He is asking for your units "1.53 what?"

HINT....
If you used an R value = 0.082, the your volume units should be in liters.