know terms:
reactants,
products, solid,
liquid, gas, aqueous,
yields
How To Balance Chemical Equations
1. Reactants go on the left hand side and products go on the right
hand side of a chemical equation. Be sure to write the correct formulas
for the reactants and products.
· Remember atoms are conserved in a chemical reaction. ie they
are neither created or destroyed. So all the atoms in the reactants
must end up somewhere among the products.
2. Count the number of atoms of each element, compound or ion in the
reactants and products. If they are not equal proceed further.
3. Balance the atoms one at a time by placing coefficients in front
of the formula so that the numbers of atoms of each element are equal
on both sides of the equation. Remember atoms may exist in an element,
compound or ion.
· It is usually easier to start with the atoms that occur in
only one substance on each side of the equation.
· Balance the atoms that occur in compounds before attempting
to balance atoms that occur in elemental form. e.g. H2,
O2 or Cl2
· To make it easier if a polyatomic ion appears unchanged on
both sides of the equation treat it as a whole unit.
· When no coefficient is written in front of a formula it is
assumed to be 1.
4. Numbers appearing in the formulas are known as subscripts. These
can never be changed when balancing the equation or you will change
the identity of the substance.
· Remember with subscripts, any number to the right of parentheses
multiplies each subscript within the parentheses.
eg Fe2(SO4)3
contains 2 Fe atoms, 3 S atoms and 12 O atoms.
5. Finally make sure that all the coefficients are in the smallest
possible whole number ratio.
Balancing
Chemical Equations (another tutorial)
When writing chemical
equations, students should already be familiar with writing chemical
formulas. We use formulas to write chemical equations. A chemical
equation is a shorthand method for describing a chemical change. The
symbols and formulas are used to indicate the substances involved
in the change. In order to balance an equation, we must know what
the reactants and products are as well as the formulas of both. The
formula of reactant(s) are found on the left hand side of the equation
and the formula of the product(s) are found on the right hand side
of the equation. The arrow is read as "yields" and the plus
sign is read as "and". When a plus sign appears on the left
side, it implies "reacts with".
Ex. A + B -------->
C + D
reactants products
Note that when
balancing chemical reactions The Law of Conservation of Mass must
be obeyed. This law states that during a chemical reaction matter
is neither created nor destroyed. What this means is that there must
be as many atoms of each type on the left-hand side as on the right-hand
side when the equation is balanced. The proper coefficients are placed
in front of the formulas in order to balance the numbers of atoms
on each side of the equation. Students should follow the steps below
in the order they are listed when balancing equations.
· Step
1. Balance all atoms other than oxygen and hydrogen
· Step 2. Balance all oxygen
· Step 3. Balance hydrogen
Remember that
subscripts in a correct formula can not be changed in order to made
an equation balance.
Balance these
equations:
1. _____Ca(OH)2(s)
+ _____HCl(aq) ---> ____CaCl2(aq) + _____H2O(l)
2. _____FeCl3(aq)
+ _____(NH4)2S(aq) --->
_____Fe2S3(s) + _____NH4Cl(aq)
3. _____KNO3
(s) ---> _____KNO2 (s) + _____O2(g)
4. _____Ag2O(s)
---> _____Ag(s) + _____O2(g)
5. _____C4H10(g)
+ _____O2(g) ---> _____CO2(g)
+ _____H2O(g)
6. _____Br2(aq)
+ _____KI(aq) ---> _____I2(aq) + _____KBr(aq)
7. _____AsCl3(aq)
+ _____H2S (aq) ---> _____As2S3
(s) + _____HCl
8. _____C5H12O
(l) + _____O2(g) --> ______CO2(g)
+ _____H2O (g)
9. _____Al(s)
+ _____H2SO4 (aq) --->
_____Al2(SO4)3(aq)
+ _____H2(g)
10. _____Fe(s)
+ _____Cl2(g) ---> _____FeCl3(s)
11. C5H12
+ O2 -----> CO2 + H2O
12. NH3
+ O2 -----> N2 + H2O
13. KOH + H2SO4
-----> K2SO4 + H2O
14. N2H4
+ N2O4 -----> N2
+ H2O
15. F2
+ H2O -----> HF + O2
16. Na2O
+ H2O -----> NaOH
17. Na2CO3
+ HNO3 -----> H2O +
CO2 + NaNO3
18. Ca3P2
+ H2O -----> PH3 +
Ca(OH)2
19. IBr + NH3
-----> NI3 + NH4Br
20. NH4NO3
-----> N2 + H2O + O2
