Question

Need answer is correct number of sig. figs. pls.

P Ta 5. A sample of helium gas has a volume of 6.50 L at a pressure of 845 mmHg and a temperature 4R78 of 25 °C. Calculate the number of moles of gas in this sample. TI

Answer 1

Given

V = Volume = 6.50 L

P = Pressure = 845 mmHg = 845/760 = 1.112 atm

T = Temperature = 25 0C = 25 + 273.15 = 298.15 K

n = number of moles of gas present in sample = ?

R = 0.0821 L.atm/mol.K

We know the ideal gas law equation

PV = nRT

then

n = PV / RT

= 1.112 atm $\times$ 6.50 L / (0.0821 L.atm/mol.K $\times$ 298.15 K)

= 0.29 mol He

So our answer is 0.29 mol He