A 22.4 liter sample of gas at STP weighs 12.0 grams. What is the molecular weight of the gas?

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32.0 g/mol

16.0 g/mol

12.0 g/mol

29.4 g/mol

d

12.0g/mole

Explanation:

Since the gas is at STP, it'll have standard values of temperature and pressure at STP

V = 22.4L

m = 12.0g

T = 273.15

P = 1.0 atm

R = 0.082 L.atm / K.mol

Using ideal gas equation,

PV = nRT

n = no. Of moles

n = PV / RT

n = (1.0 * 22.4) / (0.082 * 273.15)

n = 22.4 / 22.3983

n = 1.00

But number of moles (n) = mass (m) / molar mass (M)

n = m / M

M = m / n

M = 12.0 / 1.0

M = 12g/mol

The molar mass of the gas is 12.0g/mole

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