A sample of gas has a volume of 28.7 mL at 758 torr and 25.0oC. How many moles of gas are in this sample?

Question

A sample of gas has a volume of 28.7 mL at 758 torr and 25.0^oC. How many moles of gas are in this sample?

Answer 1

Using the ideal gas law, we can find the number of moles:

PV = nRT

P = pressure = 758 torr

V = volume = 28.7 ml x 1 L/1000 ml = 0.0287 L (note: volume should be in liters)

n = moles = ?

R = gas constant = 62.36 L torr/mol K (note: use the correct value of R to be consistent with units of pressure)

T = temperature in K = 25.0ºC + 273 = 298K

Solving for n we have

n = PV/RT = (758 torr)(0.0287 L) / (62.36 L-torr/mol-K)(298K)

n = 0.00117 moles of gas