Transcript Grams to Moles to Molecules - South Kingstown High School

Grams to Moles to Molecules
Grams to Moles to Molecules
• How many molecules in 5.00g of hydrogen
gas?
5.00g H2 x 1mole x 6.02 x 1023 molecules =
2.02 g 1 mole
= 5.00 / 2.02 x 6.02 x 1023
= 1.37 x 1024 molecules
Mole Diagram
Divide by Avogadros’s #
Divide by MM
Grams
Multiply by MM
Moles
Molecules
multiply by Avogadros’s #
Example Problems
1. How many molecules in 3.1 grams of CH4?
3.1 g CH4 x 1 mole x 6.02 x 1023 molecules =
16.04 g
1 mole
= 1.16 x 1023 molecules
How many atoms of Hydrogen are there?
1.16 x 1023 molecuels x 4 atoms of H =
= 4.64 x 1023 atoms of H
Example Problems
2. How many grams in 6.04 x 1024 molecules
of O2?
6.04 x 1024 molecules x 1 mole x 32.00 g
6.02 x 1023 molecules
1 mole
= 321 grams of O2
Molar Volume
• The molar volume of a gas is measured at
STP (standard temperature and pressure).
• The Molar Volume is 22.4 L for 1mole of
any gas.
Molar V = 22.4 L/mol
• 1 mole of gas = 6.02 x 1023 molecules
• 6.02 x 1023 molecules of any gas at STP will occupy
22.4 L (Avogadro’s principle)
• Allows you to interrelate mass, moles, pressure,
volume, and temperature for any sample of gas.
Molar Volume as a Conversion
Factor
The molar volume at STP can be used to form
conversion factors.
• What is the volume occupied by 2.75 moles
N2 gas at STP?
• The molar volume is used to convert moles
to liters.
2.75 moles N2 x 22.4 L = 61.6 L
1 mole
Learning Check
1. What is the volume at STP of 4.00 g of
CH4?
a) 5.60 L
b) 11.2 L
c) 44.8 L
2. How many grams of He are present in 8.00
L of He at STP?
a) 25.6 g
b) 0.357 g
c) 1.43
Solution
1.
4.00 g CH4 x 1 mole CH4 x 22.4 L (STP) = 5.60 L
16.0 g CH4 1 mole CH4
2.
8.00 L x 1 mole He x 4.00 g He = 1.43 g He
22.4 L
1 mole He