Question

What is the molecular weight of a gas if 0.190 g occupies 250 ml at STP?

a) 2 g/mol
b) 4 g/mol
c) 16 g/mol
d) 32 g/mol

Answer 1

The molecular weight of the gas can be calculated using the given mass and volume at STP by utilizing the molar volume of a gas. The gas has a molecular weight of approximately 17.03 g/mol, which is not an exact match to any of the multiple-choice options provided.

Step-by-step explanation:

To determine the molecular weight of a gas given its mass and volume at standard temperature and pressure (STP), we can use the molar volume of a gas at STP. The molar volume of any gas at STP is 22.4 liters per mole. Here's how we can calculate it:

1. Convert the volume of the gas to liters from milliliters (250 ml = 0.250 L).
2. Use the molar volume at STP (22.4 L/mol) to find the number of moles of gas present in the given volume (0.250 L).
3. Calculate the molecular weight by dividing the mass of the gas (0.190 g) by the number of moles calculated in step 2.

Step 1: Conversion to liters

250 ml = 0.250 L

Step 2: Calculating moles

Moles of gas = Volume of gas / Molar volume at STP
= 0.250 L / 22.4 L/mol
= 0.01116 mol (approximately)

Step 3: Calculating molecular weight

Molecular weight = Mass / Moles
= 0.190 g / 0.01116 mol
= 17.03 g/mol (approximately)