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Word Equations & Balanced Chemical Equations.
If you are doing the basic level you only need to know the word equations.
If you are doing the higher level you really ought to know the balanced chemical equations
given below.
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Aerobic respiration:
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In your tissues energy is needed for growth, repair, movement, excretion
and so on. This energy is obtained from glucose supplied to the tissues by your blood.
Aerobic respiration also requires Oxygen. The products of tissue respiration are Carbon
Dioxide and water.
Glucose + Oxygen = Carbon Dioxide + Water + Energy
| C6H12O6 |
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+ |
|
6O2 |
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= |
|
6CO2 |
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+ |
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6H2O |
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+ |
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Energy |
The first one is a word equation. All it says is glucose
and Oxygen are turned into Carbon Dioxide and water releasing energy. If you still don't
understand this, just pretend that you are a parrot and memorise it.
The second one is a balanced chemical equation.
C6H12O6
...means one molecule of glucose, but we
are much too lazy to put a figure 1 in front of the glucose molecule.
The C6
.means that the glucose molecule contains 6 atoms of
Carbon.
The H12
.means that the glucose molecule contains 12 atoms of
Hydrogen.
The O6
.means that the glucose molecule contains 6 atoms of
Oxygen.
6O2
...means 6 molecules of Oxygen, and each molecule contains
2 atoms of Oxygen.
The left-hand side of the equation shows 6 atoms of Carbon, 12 atoms of Hydrogen and a
total of 18 atoms of Oxygen. So does the right-hand side. The two sides of the equation
must balance.
6CO2
...means 6 molecules of Carbon Dioxide. The 6 multiplies
the Carbon and the Oxygen.
The C
...means one atom of Oxygen, but again we are ever so lazy
and do not bother to put a little figure 1 after the Carbon atom. So all together there
are 6 atoms of Carbon. ( 6 times 1). The same number of Carbon atoms on each side.
The O2
...means that every molecule of Carbon Dioxide contains 2
atoms of Oxygen. So all together there are 12 atoms of Oxygen. Plus the 6 atoms of Oxygen
in the water makes a total of 18. Same on both sides again.
By now you should realise that there are six molecules of water and that each contains
two atoms of Hydrogen and one atom of Oxygen. Now calculate the number of Hydrogen atoms
on the right-hand side. You should find that 6 times 2 makes 12. So the Hydrogen atoms
balance up as well.
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Photosynthesis: |
Carbon Dioxide + Water = Glucose + Oxygen
| 6CO2 |
|
+ |
|
6H2O |
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| Light |
| ...........= |
| Chlorophyll |
|
|
C6H12O6 |
|
+ |
|
6O2 |
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Here are the equations for photosynthesis. If you have
understood the aerobic respiration equations, these are easy. If you have not understood,
just learn them.
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Anaerobic respiration: |
Glucose = Ethanol + Carbon Dioxide + Energy
| C6H12O6 |
|
= |
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2C2H5OH |
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+ |
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2CO2 |
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+ |
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Energy |
This is what yeast does when it runs out of Oxygen. It does not release so much energy
and the ethanol (alcohol) is poisonous, so yeast will respire aerobically if it can. This
is just a last resort.
When we respire anaerobically we produce lactic acid instead of ethanol. It is the
lactic acid which gives us cramp. So lactic acid is also poisonous and we must try to
avoid making too much.
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