|
MAKING
SENSE OF CHEMICAL EQUATIONS
Example
2:
"magnesium ribbon
reacts vigorously with dilute hydrochloric acid to form hydrogen
gas and a solution of magnesium chloride."
Write the word equation:
magnesium
+ hydrochloric acid à magnesium chloride + hydrogen gas
Translate into symbols
and formulae:
| Mg
+ HCl |
 |
MgCl2 +
H2 |
Balance the equation:
| LHS |
RHS |
| 1 Mg |
1
Mg |
| 1 H |
2
H |
| 1 Cl |
2
Cl |
There is only one
hydrogen and one chlorine atom on the LHS but two of these
atoms on the RHS. Increase both of these on the LHS by putting
a large "2" in front of the HCl.
The balanced equation
is thus:
| Mg
+ 2HCl |
|
MgCl2 +
H2 |
Adding state symbols
gives:
| Mg(s)
+ 2HCl(aq) |
|
MgCl2(aq)
+ H2(g) |
Now try these examples
for yourself:
(A) Translate into
symbols and balance each equation:
|
1. calcium carbonate
breaks down on heating to give calcium oxide and carbon
dioxide.
|
| 2. sulphur burns
in oxygen to form sulphur dioxide gas. |
| 3. heating magnesium
and sulphur powders together produces solid magnesium sulphide. |
| 4. sodium hydroxide
and hydrochloric acid react to form sodium chloride and
water. |
| 5. hydrogen gas
and oxygen gas burn together to form water. |
| 6. zinc metal
and copper sulphate solution react to produce copper and
zinc sulphate solution. |
(B) Balance these
equations and add state symbols:
| 1.
CuO + HNO3 |
|
Cu(NO3)2 +
H2O |
| 2.
Al + Cl2 |
|
AlCl3 |
| 3.
N2 + H2 |
|
NH3 |
| 4.
Na + H2O |
|
NaOH
+ H2 |
| 5.
K2CO3 + H2SO4 |
|
K2SO4 +
H2O + CO2 |
| 6.
Fe + H2SO4 |
|
FeSO4 +
H2 |
| 7.
CH4 + O2 |
|
CO2 +
H2O |
| 8.
Pb(NO3)2 + NaCl |
|
PbCl2 +
NaNO3 |
(C) If you thought
the previous examples were all too easy now try these "little
beauties" (definetly "A" level grade A standard,
especially the last two!!!)
Balance these equations:
| 1.
MnO2 + HCl |
|
MnCl2 +
Cl2 + H2O |
| 2.
HBr + H2SO4 |
|
SO2 +
Br2 + H2O |
| 3.
HI + H2SO4 |
|
I2 +
H2S + H2O |
| 4.
KMnO4 + HCl |
|
KCl
+ MnCL2 + Cl2 +
H2O |
| 5.
FeSO4 + KMnO4 +
H2SO4 |
|
(Fe)2 (SO4)3+K2SO4+MnSO4+H2O |
Answers
|
