Equation Practice
How do balance an ionic Formula formula?
First, note that the name is in two parts ( a cation followed by an anion).
These ions will be listed with their name formula and charge on the “valency table” (Which you
promise not to lose!)
Example Iron (iii) is a cation. You will see that it is
Fe3+
Chromate is CrO42- . It is an anion. It is actually made from a group of 5 atoms and has a
charge of -2.
You must treat the group as one thing.
To write a formula for Iron (iii) Chromate:
Replace name with symbols from table.
Fe3+ CrO42The charges do not balance. Take 2 of the iron and 3 of the chromate to balance the charges
as 6+ and 6 –
Write it :
Fe2 (CrO4)3
:- we used brackets because chromate is made from more
than 1 atom. We have to keep it as a group.
Your turn! Write balance formula for the following:
I.
II.
III.
IV.
V.
Silver Phosphate
Magnesium Chloride.
Ammonium Nitride
Copper (ii)Sulphite
Aluminium carbonate.
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Equation Practice
What is a molecular Formula?
Let’s consider the formula for sugar
C12H22O11.
This means one molecule of sugar.
The molecule has 12 atoms of carbon, 12 atoms of Hydrogen, 11 atoms of oxygen.
Your turn again.
Explain the following formulas.
Acetic acid C2H4O2
Benzene C6H6
Carbon tetra chloride C Cl4
Formulas you need to Know.
Water is H2O, Carbon Dioxide is CO2, Ammonia s NH3,
Hydrogen, oxygen, Chlorine, Fluorine, Nitrogen are diatomic gases. You write the formula
with a little 2. See page 52.
Acids you need to know.
Sulphuric acid H2SO4
cation is H+
anion is SO42-
Hydrochloric acid HCl
cation is H+
anion is Cl-
Nitric acid H NO3
cation is H+
anion is NO3-
Acetic (ethanoic acid) CH3COOH
cation is H+
anion is CH3COO-
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Equation Practice
How do we balance double displacement reactions?
Not the reactants are ionic compounds. The name is two parts. cation anion.
Write the names of the two reactants in words with a + sign between.
Then swap anions to write products in words after the arrow.
Example Sodium chloride solution is mixed with silver nitrate solution.
Step 1 word equation
calcium chloride + silver nitrate  calcium nitrate + silver chloride.
Step 2 use the valence tables to write the symbols.
Ca2+ Cl -
+
Ag +NO3-

Ca2+ NO3- +
Ag+ Cl-
Step 3 balance individual formulas using charges.
Ca Cl2
+
Ag NO3

Ca (NO3)2
+
Ag Cl

Ca (NO3)2
+
2Ag Cl
Step 4 use coefficients to balance overall
Ca Cl2
+
2Ag NO3
Step 5 add states to show precipitates
Ca Cl2(aq) + 2Ag NO3(aq)  Ca (NO3)2(aq) + 2Ag Cl(aq)
Try these
Copper nitrate solution mixed with sodium carbonate solution
Potassium phosphate solution mixed with lead(ii) chloride solution
Iron (iii) nitrate solution mixed with sodium hydroxide solution
Barium nitrate solution mixed with sodium sulphate solution
Calcium chloride solution mixed with ammonium carbonate solution
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Equation Practice
Reactions with acids
The acid is like a salt where the cation is H+
If it reacts with a metal the products are salt and Hydrogen gas.
If it reacts with a carbonate or hydrogen carbonate then products are salt + carbon dioxide +
water.
If it reacts with metal oxide or metal hydroxide then products are salt + water.
Try these
Hydrochloric acid + magnesium metal
Nitric acid + copper carbonate
Sulphuric acid + lead (ii) oxide
Acetic acid + sodium Hydrogen carbonate.
Nitric acid + Zinc metal
Hydrochloric acid + calcium Hydroxide.
Single Displacement
Metal 1 + Metal 2 salt  metal 2 + metal 1 salt
Try these
Copper metal + silver nitrate
Iron metal + copper chloride
Magnesium metal + nickel nitrate.
Combustion practice
Write balances reactions for the following burnt in air.
Ethanol (C2H6O), Pentane (C5H12), propanol (C3H8O)
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