Wednesday, April 15, 2009


Key Concepts

  • Empirical Formula of a compound shows the ratio of elements present in a compound.
  • Molecular Formula of a compound shows how many atoms of each element are present in a molecule of the compound.
  • The empirical formula mass of a compound refers to the sum of the atomic masses of the elements present in the empirical formula.
  • The relative molecular mass (formula mass, formula weight or molecular weight) of a compound is a multiple of the empirical formula mass.
    RMM = n x empirical formula mass
  • Empirical Formula can be calculated from the percentage (or percent) composition of a compound.
Molecular formulas and empirical formulas are sometimes the same: Molecular formulas and empirical formulas are not always the same:
    The molecular formula for hydrogen peroxide is H2O2, a 1 to 1 ratio.
    The formula is correct. Remember that peroxide is a polyatomic ion with a charge of -2.
    Reduce the subscripts to the lowest form.
    The empirical formula for hydrogen peroxide is HO, a 1 to 1 ratio.
Calculating Empirical Formulas:
    Subscripts in a chemical formula are usually thought of as a ratio of atoms.
    Subscripts can also be thought of as a ratio of moles . . . . .
    a mole being the number of atoms needed
    to equal the atomic mass number of an element.

    To determine an empirical formula, one must determine the mole ratio.

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SPM Chemistry Form 4

Form 4 Chemistry
1. Introduction To Chemistry
1.1 Understanding chemistry and its importance
1.2 Synthesising scientific method
1.3 Incorporate scientific attitudes and values in conducting scientific investigations
2. The Structure Of The Atom
2.1 Analysing matter
2.2 Changes in the state of matter
2.3 Synthesising atomic structure
2.4 Understanding isotopes and assessing their importance
2.5 Understanding the electronic structure of an atom
3. Chemical Formulae And Equations
3.1 Understanding and applying the concepts of relative atomic mass and relative molecular mass
3.2 Analysing the relationship between the number of moles with the number of particles
3.3 Analysing the relationship between the number of moles of a substance with its mass
3.4 Analysing the relationship between the number of moles of a gas
3.5 Synthesising chemical formulae
3.6 Interpreting chemical equations
4. Periodic Table of Elements
4.1 Analysing the Periodic Table of Elements
4.2 Analysing Group 18 elements
4.3 Analysing Group 1 elements
4.4 Analysing Group 17 elements
4.5 Analysing elements in a period
4.6 Understanding transition elements
5. Chemical Bonds
5.1 Understanding formation of compounds
5.2 Synthesising ideas on formation of ionic bond
5.3 Synthesising ideas on formation of covalent bond
5.4 Analysing properties of ionic and covalent compounds
6. Electrochemistry
6.1 Understanding properties of electrolytes and non-electrolytes
6.2 Analysing electrolysis of molten compounds
6.3 Analysing the electrolysis of aqueous solutions
6.4 Evaluating electrolysis in industry
6.5 Analysing voltaic Cell
6.6 Synthesising electrochemical series
7. Acids And Bases
7.1 Analysing characteristics and properties of acids and bases
7.2 Synthesising the concepts of strong acids, weak acids, strong alkalis and weak alkalis
7.3 Analysing concentration of acids and alkalis
7.4 Analysing Neutralization
8. Salt
8.1 Synthesising Salts
8.2 Synthesising qualitative analysis of salts
8.3 Practising to be systematic and meticulous when carrying out activities
9. Manufactured Substances in Industry
9.1 Understanding the manufacture of sulphuric acid
9.2 Synthesising the manufacture of ammonia and its salts
9.3 Understanding Alloys
9.4 Evaluating uses of synthetic polymers
9.5 Applying uses of glass and ceramics
9.6 Evaluating uses of composite materials

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