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Calderglen High School
1
What is the CHEMICAL FORMULA
of a substance?
answer
The ratio of atoms of each element
in the substance
Calderglen High School
2
What is a molecule?
answer
A group of atoms joined
together by covalent
bonds
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3
What is the molecular formula for this molecule?
answer
C2H6O
H H
H
C
C
H
H
O
H
Calderglen High School
4
What is the correct formula for this molecule?
answer
H
C
Cl
Cl
CHCl3
Cl
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5
What is the chemical formula of
hydrogen?
answer
H2
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6
How many atoms of each element
are present in a molecule of H2O?
answer
H=2
O=1
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How many atoms of each element are
7 present in a molecule of C H O ?
6 12 6
answer
C=6
H = 12
O=6
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8
What is meant by the prefix:Mono?
answer
Mono = 1
ie carbon monoxide molecules
contain one oxygen atom (CO)
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9
What is meant by the prefix:Di?
answer
Di = 2
ie carbon dioxide molecules
contain two oxygen atoms (CO2)
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10
What is meant by the prefix:Tri?
answer
Tri = 3
ie sulphur trioxide molecules
contain three oxygen atoms (SO3)
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11
What is meant by the prefix:Tetra?
answer
Tetra = 4
ie carbon tetrachloride molecules
contain four chlorine atoms (CCl4)
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12
What is the chemical formula of
carbon tetrachloride?
answer
CCl4
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13 Use the prefix method to name the
compound with the formula N2O4
answer
Dinitrogen
tetroxide
(tetraoxide)
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14
What is VALENCY?
answer
Valency = combining power of an atom
Group 1 2 3 4 5 6 7 8
Valency 1 2 3 4 3 2 1 0
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15
What is the valency of the
Group 7 elements?
answer
1
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16
What is the valency of the
Group 2 elements?
answer
2
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17
Describe how to work out the
chemical formula of a compound?
Symbols
Valencies
answer
Swap
Divide
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18
What is the chemical formula of
hydrogen sulphide?
answer
Symbols
Valencies
H
S
1
2
Swap
2
1
Divide
not needed here
ANSWER:
H2 S
Calderglen High School
19
What is the chemical formula of
calcium oxide?
Symbols
Valencies
Ca O
2
2
Swap
2
2
Divide
21
answer
ANSWER:
CaO
21
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20
Write the formula for silver (I) chloride
answer
Symbols
Valencies
Ag
Cl
1
1
Swap
1
1
Divide
not needed here
ANSWER:
AgCl
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21
What is the valency of iron
in iron (III) oxide?
answer
3
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22
How is the valency of a
transition metal shown in the
names of its compounds?
answer
Roman Numerals in brackets
eg copper (II) chloride =
valency 2
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