# How many molecules are there in 4.00 L of oxygen gas at 500 C and 50.0 Torr

If someone would check and or correct my work that would be appreciated.

Q: How many molecules are there in 4.00 L of oxygen gas at 500 C and 50.0 Torr

PV=nRT

50 torr = .066 atm

500 C = 773 K

And the constant would be .0821

0.066 x 4 = moles x 0.082 x 773

therefore there are 0.004 moles x 6.02 x 10^23

So there are 2.51 x 10^21 molecules

• (Pressure in atmospheres) * (Volume in liters) = (number of moles) * (Ideal gas constant) * (Temperature in ˚K)

1 atm = 760 torr, P = 50/760 atm

V = 4.00 L

Ideal gas constant = 0.0821

T = 500 + 273 = 773˚K

50/760 * 4.00 = n * 0.0821 * 773

n = (50/760 * 4.00) ÷ (0.0821 * 773)

This is the number of moles of oxygen in the container.

1 mole = 6.02 * 10^23 molecules

Number of molecules = 6.02 * 10^23 * Number of moles

Number of molecules = 6.02 * 10^23 * (50/760 * 4.00) ÷ (0.0821 * 773)

Number of molecules ≈ 2.496 * 10^21

Rounded to 3 significant digits, the answer is 2.50 * 10^21 molecules.

This is the number of molecules of oxygen in the container.

I suggest that you do not round your answers as you calculate.

• ans. is correct!

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