A 0.744 g sample of sulfur hexafluoride gas at 61oC occupies a volume of 0.764 L, what is the pressure in torr? Answer needs to be rounded to 3 sig figs.

Question

I don't know how to do the Ideal Gas law and need help.

Answer 1

How to use the ideal gas law PV = nRT

Simply fill in the known values and solve for the unknown.

Known:

n = moles = 0.744 g SF6 x 1 mol SF6/146 g = 0.00510 moles (not exactly known but can be calculated)

V = volume = 0.764 L

T = temperature in K = 61 + 273 = 334K

R = gas constant = 62.36 L-torr/Kmol (you could use 0.0821 but the question asks for P in torr)

Unknown:

P = pressure in torr

Solving the ideal gas law for P, we have..

P = nRT/V = (0.00510)(62.36)(334) / 0.764

P = 139 torr (3 sig. figs.)

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If you used R = 0.0821 Latm/Kmol you'd have to later convert the answer to torr as follows:

P = (0.00510)(0.0821)(334) / 0.764 = 0.183 atm

Converting atm to torr we have...

0.183 atm x 760 torr / 1 atm = 139 torr (same answer as above).

Answer 2

this video will help you get the right answer

https://youtu.be/2spz4y7iTBs