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CHEMICAL REACTIONS
During a chemical reaction, bonds are broken and formed as molecules and atoms
combine and rearrange to form new substances.
A chemical equation is a sentence that uses chemical formulas and symbols to tell us
what happens during a chemical reaction.
REACTANTS
PRODUCTS
2H2 (g) + O2(g) → 2 H2O(l)
HOW CAN YOU TELL IF A CHEMICAL REACTION IS OCCURRING?
1.
2.
3.
4.
5.
SYMBOLS USED IN CHEMICAL EQUATIONS
Symbol
Explanation
+
(s) or ↓
(l)
(g)
(aq)
Catalyst
Writing Chemical Equations
1.
a.
b.
c.
d.
e.
f.
Write formulas and other symbols for these substances:
metallic potassium
sodium chloride dissolved in water
heat supplied to a chemical reaction
liquid mercury
zinc chloride as a catalyst
carbon dioxide gas
2. Write a skeleton equation for each of these chemical reactions:
a. Aluminum metal reacts with oxygen in the air to form solid aluminum oxide.
b. When solid mercury (II) sulphide is heated in the presence of oxygen, liquid
mercury metal and gaseous sulphur dioxide are produced.
c. Oxygen gas can be made by heating potassium chlorate in the presence of the
catalyst manganese dioxide. Potassium chloride is left as a solid residue.
3. Write sentences that completely describe each of the chemical reactions shown
in these skeleton equations.
a. BaCl2 (aq) + H2SO4 (aq) → BaSO4 (s) + HCl (aq)
b. NH3 (g) + O2 (g) → NO (g) + H2O (g)
c. N2O3 (s) + H2O → HNO2 (aq)
d. K(s) + H2O → KOH (aq) + H2 (g)
e. NaOH (aq) + HNO3 (aq) → H2O + NaNO3 (aq)
f. FeO(s) + C(s)
Fe (s) + CO (g)