Download Chemical Equations

Chapter 4
: CHEMICAL REACTIONS
Reactants: Zn + I2
Product: Zn I2
Feb. 17, 2006
Chemical Equations
Depict the kind of reactants and
products and their relative amounts
in a reaction.
4 Al(s) + 3 O2(g) → 2 Al2O3(s)
The numbers in front are called
stoichiometric coefficients
The letters (s), (g), and (l) are the
physical states of compounds (solid,
liquid or gas).
Feb. 17, 2006
1
Chemical Equations
4 Al(s) + 3 O2(g)
→ 2 Al2O3(s)
This equation means
4 Al atoms + 3 O2 molecules
give→
2 molecules of Al2O3
4 moles of Al + 3 moles of O2
give→
2 moles of Al2O3
Feb. 17, 2006
Chemical Equations
• Because the same
atoms are present in a
reaction at the
beginning and at the
end, the amount of
matter in a system
does not change.
• This is the Law of the
Conservation of Matter
Screen 4.3 on CD-ROM
Feb. 17, 2006
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Chemical Equations
Because of the principle of the conservation
of matter,
an equation must be balanced.
It must have the same number of atoms of the
same kind on both sides.
2 Al(s) + ___
3 Br2(liq) →___
1 Al2Br6(s)
___
Feb. 17, 2006
Balancing Equations
5 O2(g)
1 3H8(g) + _____
____C
3
4
_____CO
2(g) + _____ H2O(g)
11 O2(g)
2 B4H10(g) + _____
____
4 B2O3(g) + _____
10 H2O(g)
_____
Feb. 17, 2006
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