C2.5 10b
Empirical and molecular formulae
F
Name
Element
aluminium
bromine
calcium
carbon
chlorine
Class
Symbol
Al
Br
Ca
C
Cl
Ar
27
80
40
12
35.5
Element
copper
fluorine
hydrogen
iodine
Symbol
Cu
F
H
I
Ar
64
19
1
127
Date
Element
iron
oxygen
sodium
sulphur
Symbol
Fe
O
Na
S
Ar
56
16
23
32
1 Complete the table.
Mr
42
Molecular formula
Empirical formula
CH2
C5H10
C 4H 8
44
C 3H 8
78
CH
H 2O 2
2 Write the empirical formula of each of the following substances.
a C2H6
b P2O3
d C6H12
e C2H4O2
g C6H10
h C12H22O11
c SO2
f C2H7N
3 Find the empirical formula of each of the following substances using the data about composition
by mass.
a Ca 20%, Br 80%
b Fe 77.8%, O 22.2%
c Al 0.364 g, Cl 1.436 g
d C 13.6%, F 86.4%
e C 3.31 g, H 0.69 g
f Na 43.4%, C 11.3%, O 45.3%
g Ca 0.642 g, H 0.032 g, C 0.385 g, O 1.541 g
4 a2.67 g of copper reacts with sulphur to form 4.01 g of copper sulphide. Find the empirical
formula of copper sulphide.
b 3.53 g of iron reacts with chlorine to form 10.24 g of iron chloride. Find the empirical formula for
the iron chloride.
170
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