SME
Grade 10 Science · Chemistry
The mole and molar mass
Use this for “How many moles and molecules are in 9.01 g of water?”
Diagram
Mass = 0.5 mol × 18.02 g/mol = 9.01 g.
Particles = 0.5 mol × 6.022 × 10²³ = 3.011 × 10²³.
Every path goes through moles: the filled box is the value given.
This is an example. Type your own values to start a new problem.
m
g
÷
M
g/mol
=
n
mol
N
Particles
calculated
Formulas
m
=
n
×
M
9.01 = 0.5 × 18.02
N
=
6.022 ×
10
23
×
n
3.01 ×
10
23
=
6.022 ×
10
23
×
0.5
Assumptions
•
One mole is 6.022 × 10²³ particles.
•
Molar mass is the formula’s atomic masses added, in g/mol: water is 18.02 g/mol.
•
Every conversion goes through moles.
Step-by-step
WE KNOW
m = 9.01 g, M = 18.02 g/mol
FIND
amount (n), particles (N)
Step 1 · Find amount (n)
Use m = n × M
Divide the grams by the grams in one mole.
n
=
m
M
n
=
9.01/18.02
n
=
0.5
mol
Step 2 · Find particles (N)
Use N = 6.022 × 10²³ × n
One
mole
is
6.022 ×
10
23
particles.
N
=
6.022 ×
10
23
×
0.5
N
=
3.01 ×
10
23
Check
Put the numbers back in. Both sides should match.
9.01 = 0.5 × 18.02 ✓
3.01 ×
10
23
≈
6.022 ×
10
23
×
0.5
✓
Topic check
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