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Writing
and balancing equations
Francine
Taylor Campbell, Contributor
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| Cornwall
College students, Shavon Farrero
and André Bernard, do a
presentation of Marcus Garvey
on Garveism during the Re-enactment
of Proclamation Day Civic Ceremony
in Sam Sharpe Square, Montego
Bay, on October 3, 2004. The ceremony
was a part of the Montego Bay
25th City Status Anniversary celebrations.
Claudine Housen
Photo |
IN
THIS lesson, we intend to look at writing
and balancing chemical equations, as
this topic is crucial in understanding
chemistry.
First
of all, an equation is a representation
of a reaction.
An
equation should show the reactants
and products taking part in a chemical
reaction and should show in what ratio
these products combine.
In
writing an equation, the first step
is to express it in word form.
This ensures that all reactants and
possible products are accounted for.
The second step is to express the
word equation in symbols. Here,
the correct formula for each
reactant and product must be given.
The
final step is to check that the same
number of atoms of a given element
or their ions are on each side. When
this is done, the equation is said
to be balanced. State symbols are
also added to the equation.
Now
let us examine the following questions:
1.
Write an equation for the reaction
between calcium oxide and water.
Water
+ Calcium oxide = Calcium hydroxide
(word)
H2O
(l) + CaO (s) = Ca(OH)2 (aq) (formula)
Checking
the number of atoms of each element
on both sides
2
H 2 H
2
O 2 O
1
Ca 1 Ca.
This
equation is balanced.
2.
Write an equation for the reaction
between sodium carbonate and hydrochloric
acid.
Sodium
carbonate + Hydrochloric acid = Sodium
chloride + carbon dioxide + water
Na2CO3
(s) + HCl (aq) = NaCl + CO2 (g) +
H2O (l)
Checking
both sides:
2
Na 1 Na
1
C 1 C
3
O 3 O
1
H 2 H
1
Cl 1 Cl
To
balance this equation, 2 can be placed
before the Na atom to have 2 Na atoms
on both sides.
Na2CO3
(s) + HCl (aq) = 2NaCl + CO2 (g) +
H2O (l)
This
means we now have 2 Cl on one side
and 1 Cl on the other side.
Placing
a 2 before HCl will balance this.
Na2CO3
(s) + 2HCl (aq) = 2NaCl + CO2 (g)
+ H2O (l) (balanced).
3.
Write an equation for the reaction
between sodium hydroxide and phosphoric
acid.
Sodium
Hydroxide + Phosphoric acid = Sodium
phosphate + water
NaOH
(aq) + H3PO4 (aq) = Na3PO4 (aq) +
H2O (l)
Checking
sides:
1
Na 3 Na
5
O 5 O
4
H 2 H
1
P 1 P
Put
3 in front of NaOH to balance the
Na
3NaOH
(aq) + H3PO4 (aq) = Na3PO4 (aq) +
H2O (l)
This
now creates 6 H = 2 H, which can be
balanced by multiplying the 2 H by
3.
3NaOH
(aq) + H3PO4 (aq) = Na3PO4 (aq) +
3H2O (l) (Balanced)
Now
attempt the following:
4.
Ammonia reacts with oxygen in air
to produce nitrogen and water. Write
a balanced equation for this reaction.
5.
Iron III oxide reacts with carbon
monoxide to produce iron and carbon
dioxide.
6.
Calcium hydroxide and ammonium chloride
reacts to give calcium chloride, water
and ammonia.
*
Francine Taylor-Campbell is
an independent contributor.
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