learning objectives: to be able to calculate m r values from a r values
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Learning Objectives:• To be able to calculate Mr values from Ar values
Calculating Mr Values from Ar Values
Masses of MoleculesExampleH2 contains 2 x hydrogen atoms.
Hydrogen atoms have a relative mass of 1, so H2 has a relative mass of:
H H HH
mass = 1 mass = 1 H2
2 x 1 = 2g
Masses of MoleculesExampleCO2 contains 1 x carbon atom and 2 x oxygen atoms.carbon atoms have a relative mass of 12, and oxygen atoms have a relative mass of 16.
The sum is: (1 x 12) + (2 x 16)= 12 + 32= 44g
CO O
16 12 16
Calculate the Mr values of the following:
N2 Al2O3
NH3 CaCO3
H2O NaNO3
MgO NH4NO3
NaOH CuSO4
Na2O Fe2O3
C2H6 HNO3
H2SO4 F2O
28
Reset
17
18
40
40
62
30
98
102
100
85
80
160
160
63
54
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Extension Activity (find the Mr of these compounds)
Mg(OH)2
(NH4)2SO4
Fe(OH)3
1 x Mg + 2 x O + 2 x H= 24 + (2 x 16) + (2 x 1)
= 58
1 x Fe + 3 x O + 3 x H= 56 + (3 x 16) + (3 x 1)
= 107
2 x N + 8 x H + 1 x S +4 x O= (2 x 14) + (8 x 1) + 32 + (4 x 16)
= 132
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