Word equations describe chemical reactions using words.
Word equations have the following pattern:
name of reactant 1( ) + name of reactant 2( ) + ...
name of product 1( ) + name of
product 2( ) + ...
The reactants are the substances with which you begin the reaction. The names of the
reactants are listed before the arrow in the word equation. A plus sign is used between the
reactants when there is more than one reactant.
The products are the substances made as a result of the reaction. The names of the
products are listed after the arrow in the word equation. A plus sign is used between the
products when there is more than one product.
Sometimes heat or energy is needed or formed in a reaction. Heat or energy is included in
the word equation just like any other reactant or product.
Behind the name of each reactant and product you give the state of the substance in
brackets using the shortform indicated here:





solid (s)
liquid (l)
gas (g)
aqueous (aq) This means aqueous which means that the substance was dissolved
in water or that it is in solution form.
A precipitate is an insoluble solid formed during a chemical reaction with
solutions. So (s) is used.
Examples:
1. Magnesium metal burns in oxygen gas with a bright white light to make a white powder called
magnesium oxide. magnesium (s) + oxygen (g) magnesium oxide (s) + heat
2. A solution of sodium iodide is added to a solution of potassium nitrate to make a potassium iodide
precipitate and a sodium nitrate solution.
sodium iodide (aq) + potassium nitrate (aq)
potassium iodide (s) + sodium nitrate (aq)
3. Gaseous hydrogen and gaseous oxygen react explosively to form water vapor.
hydrogen (g) + oxygen (g)
water (g) + heat
Practice:
Baking soda added to vinegar (acetic acid) makes dissolved sodium acetate, bubbles of
carbon dioxide gas and water.
In a lighter, the butane combine with the air to form carbon dioxide gas and water vapor.
When calcium hydroxide reacts with hydrochloric acid in water, dissolved calcium
chloride and water are formed. This reaction gives off heat.
Exercise
1. aqueous sodium chloride reacts with aqueous lead (II) nitrate to yield a lead (II)
chloride precipitate and aqueous sodium nitrate
2. aqueous barium nitrate reacts with sulfuric acid [H2SO4(aq)] to yield a barium sulfate
precipitate and nitric acid [HNO3(aq)]
3. silver nitrate reacts in solution with potassium chromate to yield a silver chromate
precipitate and soluble potassium nitrate
4. solid calcium carbonate reacts with hydrochloric acid [HCl(aq)] to yield aqueous
calcium chloride, carbon dioxide gas, and liquid water
5. aqueous zinc chloride reacts with dihydrogen monosulfide gas to yield a zinc sulfide
precipitate and hydrochloric acid
6. magnesium nitrate reacts in solution with potassium hydroxide to yield a magnesium
hydroxide precipitate and soluble potassium nitrate
7. solid aluminum hydroxide reacts with nitric acid to yield soluble aluminum nitrate and
liquid water
8. aqueous lead (IV) nitrate reacts with aqueous sodium sulfate to yield a lead (IV)
sulfate precipitate and soluble sodium nitrate
9. aqueous sodium hydroxide reacts with carbon dioxide gas to yield soluble sodium
carbonate and liquid water
10. solid magnesium oxide reacts with hydrochloric acid to yield a solution of
magnesium chloride and liquid water
11. solid zinc metal reacts with sulfuric acid to yield aqueous zinc sulfate and hydrogen
gas
12. solid iron (III) oxide reacts with solid aluminum metal to yield solid aluminum oxide
and solid iron metal