1. Chemical Equations
A Balancing Act

2. Propane has three atoms of carbon and eight atoms of hydrogen
Propane has three atoms of carbon and eight atoms of hydrogen. What is propane's chemical formula?
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3. C3H8

4. List the elements in this compound: H2SO4
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5. H2SO4
Hydrogen – 2 atoms
Sulfur – 1 atom
Oxygen – 4 atoms

6. What does a chemical equation tell us?9 8 10 20 30 7 5 2 3 4
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7. Chemical equations tell us how many atoms or molecules react with each other and how much of a substance is needed to react properly with another.

8. A student wrote the following equation: 4Al + 3O2 2Al2O3
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9. In this reaction, aluminum reacts with oxygen to form 2Al2O3.

10. What do coefficients & subscripts show us in chemical formulas?9 8 10 20 30 7 5 2 3 4
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11. 6 – H, 3 – S, 12 - 9 Coefficients – the number of molecules
Subscripts – the number of atoms
No number is understood to be “1”
3H2SO4 =
H2SO4
6 – H, 3 – S,
H2SO4 =
2 – hydrogen
1 – Sulfur
4 – Oxygen
subscript
coefficient

12. Identify the reactants, products, subscripts, and coefficients in this chemical equation:
6 CO2 + 6 H2O + light → C6H12O6 + 6 O2 9 8 10 20 30 7 5 2 3 4
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13. Carbon Dioxide + Water + Light energy → Glucose + Oxygen
6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
Coefficients
Subscripts
Carbon Dioxide + Water + Light energy → Glucose + Oxygen
Reactants:
CO2
H2O
light
Products:
C6H12O6 O2

14. CHEMICAL EQUATIONS
A chemical equation describes what happens in a chemical reaction.
The equation identifies the reactants (starting materials) and products (resulting substance)
For example, we know that hydrogen gas and oxygen gas can react to form water. A chemical equation for the production of water is;
H2 + O2 –› 2H2O
Reactants = 2 atoms of Hydrogen & 2 atoms of Oxygen
Product = 2 water molecules

15. Law of Conservation of Mass
Matter cannot be created nor destroyed; there are no more atoms at the end of a chemical reaction than there were at the beginning.

16. Law of Conservation & Balancing Chemical Equations
When you react 2 molecules of hydrogen gas (H2) with 1 molecule of oxygen gas (O2), you will get 2 molecules of water (H2O):
2 H2 +  O2 –› 2 H2O
Notice in the equation above that you started with 4 atoms of hydrogen and 2 atoms of oxygen, and you ended with 4 atoms of hydrogen and 2 atoms of oxygen.

17. Balancing Chemical Equations