Download 58 the mole

The mole
1
One mole of any substance is defined as the formula mass in grams, i.e. the gram formula
mass.
The formula mass of any substance is first calculated from the formula.
To calculate the mass of one mole of the substance, simply change the units to grams.
Example 1:
What is the mass of one mole of sodium?
Step 1
Symbol
Na
Step 2
Find the relative atomic mass
23
Step 3
Change units to grams
23 g
Example 2:
What is the mass of one mole of potassium sulphate, K2SO4?
Step 1
Formula
Step 2
Find the relative atomic masses
K2SO4
K
S
O
39
32
16
39 x 2
32 x 1
16 x 4
Step 3
Multiply by the number
of atoms
Step 4
Do the sum
Step 5
Formula mass
174
Step 6
Change units to grams
174 g
Chemical Changes and Structure
78
+
32
+
64
Chemical calculations 2
The mole
2
Example 3:
What is the mass of two moles of sodium chloride?
Step 1
Formula
Step 2
Find the atomic masses
Na
23
Step 3
Multiply by the number
of atoms
23 x 1
Step 4
Do the sum
23
Step 5
Formula mass
58.5
Step 6
Change units to grams
58.5 g
Step 7
Complete calculation
NaCl
Cl
35.5
35.5 x 1
+
35.5
1 mol
1
58.5 g
2 mol
1
117 g
Example 4:
How many moles are there in 36g of water, H2O?
Step 1
Formula
Step 2
Find the relative atomic masses
H
1
Step 3
Multiply by the number
of atoms
2x1
Step 4
Do the sum
Step 5
Formula mass
18
Step 6
Change units to grams
18 g
Step 7
Complete calculation
Chemical Changes and Structure
H2 O
2
O
16
16 x 1
+
16
1 mol
1
18 g
2 mol
1
36 g
Chemical calculations 2
The mole
3
Calculate the mass of one mole of each of the following elements.
(Remember that some elements exist as diatomic molecules.)
silicon
magnesium
copper
Chemical Changes and Structure
hydrogen
neon
bromine
Chemical calculations 2
The mole
4
Calculate the mass of one mole of each of the following compounds.
LiF
H2S
C3H8O
K2SO4
NaNO3
Ca(OH)2
CH2CCl2
(NH4)2CO3
Chemical Changes and Structure
Chemical calculations 2
The mole
5
Calculate the mass of each of the following substances.
2 mol of C
0.5 mol of Mg
3 mol of H2
0.2 mol of KF
2 mol of Cu2O
0.4 mol of NCl3
5 mol of Na2SO4
0.1 mol of (NH4)3PO4
Chemical Changes and Structure
Chemical calculations 2
The mole
6
Calculate the number of moles that are contained in each of the following substances.
20 g of Ca
54 g of H2O
14 g of N2
10 g of CaCO3
10.1 g of KNO3
6.4 g of SO2
6.6 g of (NH4)2SO4
18 g of sugar (C12H22O11)
Chemical Changes and Structure
Chemical calculations 2