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Chemical Foemulae and Equation
Chemical Formula
A chemical formula is a symbol use to show the type of elements and quantity of element that present in a chemical substance.
Example:
Formula of water is H2O.
The formula shows that
- There are 2 hydrogen atoms and 1 oxygen atom present in 1 water molecule.
Empirical Formula
An empirical formula is a chemical formula that gives the simplest whole-number ratio of each element in a molecule.
Example:
A glucose molecule consist of 6 carbon atoms, 12 hydrogen atom and 6 oxygen atoms.
The ratio of carbon:hydrogen:oxygen = 6:12:6
The simplest ration = 1:2:1
Therefore, the empirical formula of glucose is CH2O
Answer:
| Element | Carbon (C) | Hydrogen(H) |
| Percentage | 85.7% | 14.3% |
| Mass in 100g | 85.7g | 14.3g |
| Number of mole | 85.7/12=7.142 mol | 14.3/1 = 14.3 |
| Simple ratio | 7.142/7.142 = 1 | 14.3/7.142 = 2 |
The simplest ration of Carbon and Hydrogen is 1:2. Therfore the empirical formula = CH2
Molecular Formula
A molecular formula is a chemical formula that shows the actual number of each element in a molecule.
Constructing Chemical Formula
2 Requirements to form the formula of an ionic compound
- Have at least 2 types of ions that contain opposite charge.
- The amount of positive charge/charges must be equal to the amount of negative charge/charges in the compound.
Example:
1 Magnesium ion combine with 2 chloride ions to form 1 magnesium chloride formula.
Chemical Equation
A chemical equation is a precise description of a chemical reaction.
Example:
2 sodium atoms react with 2 water molecules to form 2 sodium hydroxide molecule and 1 hydrogen molecule.
Equantion: 2Na + 2H2O ---> 2NaOH + H2
Reactants: Na and H2O
Products: NaOH and
H2
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