2.1.2: compounds, formulae and equations

Question 1

which ions have a charge of +1?

Answer 1

all group 1 elements:
hydrogen, H
lithium, Li
sodium, Na
potassium, K
rubidium, Rb
caesium, Cs
francium, Fr

silver, Ag
gold, Au
ammonium, NH4

Question 2

which ions have a charge of +2?

Answer 2

all group 2 elements
beryllium, Be
magnesium, Mg
calcium, Ca
strontium, Sr
barium, Br
radium, Ra

iron (||), Fe
copper (||), Cu
zinc, Zn
tin, Sn
lead, Pb

Question 3

what ions have a charge of +3?

Answer 3

all group 3 elements:
boron, B
aluminium, Al
gallium, Ga
indium, In
thallium, Tl

iron (|||), Fe

Question 4

what ions have a charge of +4?

Answer 4

carbon, C
silicon, Si
tin (||||), Sn
lead (||||), Pb

Question 5

which ions have a charge of -3?

Answer 5

all group 5 elements:
nitrogen, N
phosphorus, P
arsenic, As

phosphate, PO4 3-

Question 6

which ions have a charge of -2?

Answer 6

all group 6 elements:
oxygen, O
sulphur, S
selenium, Se

carbonate, CO3 2-
sulphate, SO4 2-

Question 7

which ions have a charge of -1?

Answer 7

all group 7 elements:
fluorine, F
chlorine, Cl
bromine, Br
iodine, I
astatine, At

nitrate, NO3 -
hydroxide, OH -

Question 8

what’s the formula of lithium sulphate?

Answer 8

1. identify ionic charges of the two ions
   Li+ and SO4 2-
2. combine to get a neutral compound
   Li+ and Li+ and SO4 2-

formula = Li2SO4

Question 9

what is the formula of calcium phosphate?

Answer 9

Ca 2+ and PO4 3-

Ca 2+ and Ca 2+ and Ca 2+ and PO4 3- and PO4 3-

Ca3(PO4)2

Question 10

write the ionic equation for:

Pb(NO3)2 (aq) + 2NaCl (aq) –> PbCl2 (s) + 2NaNO3 (aq)

Answer 10

separate (aq) solutions into ions

Pb 2+ (aq) + 2NO3- (aq) + 2Na+ (aq) + 2Cl- (aq) –> PbCl2 (s) + 2Na+ (aq) + 2NO3- (aq)

cancel out spectator ions

Pb 2+ (aq) + 2Cl- (aq) –> PbCl2 (s)

Question 11

why do we write ionic equations?

Answer 11

to show the key changes in a reaction

Question 12

what are spectator ions?

Answer 12

ions that are not changing in state or in oxidation number

Question 13

what charge does hydroxide (OH) have?

Answer 13

-1

Question 14

what charge does nitrate (NO3) have?

Answer 14

-1

Question 15

what charge does phosphate (PO4) have?

Answer 15

-3

Question 16

what charge does carbon have?

Answer 16

+4

Question 17

what charge does ammonium (NH4) have?

Answer 17

+1

Question 18

what charge does aluminium have?

Answer 18

+3

Question 19

what charge does fluorine have?

Answer 19

-1

Question 20

what charge does chlorine have?

Answer 20

-1

Question 21

what charge does oxygen have?

Answer 21

-2

Question 22

what charge does sulphur have?

Answer 22

-2

Question 23

what charge does nitrogen have?

Answer 23

-3

Question 24

what charge does phosphorus have?

Answer 24

-3

Question 25

what charge does carbonate (CO3) have?

Answer 25

-2

Question 26

what charge does sulphate (SO4) have?

Answer 26

-2