Question 2 (4 points)

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

a



32.0 g/mol

16.0 g/mol

12.0 g/mol

29.4 g/mol

Molecular weight = 12.0 g/mol

The 3th option is correct

Explanation:

Step 1: Data given

Volume of a gas = 22.4 L

STP = 1 atm and 273 K

Mass of the gas = 12.0 grams

Step 2: Calculate moles of the gas

p*V = n*R*T

⇒with p = the pressure of the gas = 1.0 atm

⇒with V = the volume of the gas = 22.4 L

⇒with n = the number of moles = TO BE DETERMINED

⇒with R = the gas constant = 0.08206 L*Atm/mol*K

⇒with T = the temperature = 273

n = (p*V)/ (R*T)

n = (1* 22.4)/ (0.08206 * 273)

n = 1.00 moles

Step 3: Calculate molecular weight of the gas

Molecular weight = mass of the gas / moles of gas

Molecular weight = 12.0 grams / 1.00 moles

Molecular weight = 12.0 g/mol

The 3th option is correct

first one is the correct answer