# CHEMISTRY SEMESCO

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## 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.

# SPM Chemistry Form 4

 Form 4 Chemistry 1. Introduction To Chemistry1.1 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 Atom2.1 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 Equations3.1 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 Elements4.1 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 Bonds5.1 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. Electrochemistry6.1 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 Bases7.1 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. Salt8.1 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 Industry9.1 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

# SPM Chemistry Form 5

 Form 5 CHEMISTRY 1. Rate Of Reaction1.1 Analysing rate of Reaction1.2 Synthesising factors affecting the rate of reaction1.3 Synthesising ideas on collision theory1.4 Practising scientific knowledge to enhance quality of life 2. Carbon Compounds2.1 Understanding carbon compounds2.2 Analysing Alkanes2.3 Analysing Alkenes2.4 Synthesising ideas on isomerism2.5 Analysing Alcohols2.6 Analysing carboxylic acids2.7 Analysing esters2.8 Evaluating fats2.9 Analysing natural Rubber2.10 Creating awareness of order in homologous series2.11 Expressing gratefulness for the variety of organic materials in nature 3. Oxidation And Reduction3.1 Analysing redox Reactions3.2 Analysing rusting as a redox reaction3.3 Understanding the reactivity series of metals and its application3.4 Analysing redox reactions in electrolytic and chemical cells3.5 Appreciating the ability of elements to change their oxidation numbers 4. Thermochemistry4.1 Evaluating energy changes in chemical reactions4.2 Understanding heat of precipitation4.3 Understanding heat of displacement4.4 Understanding heat of neutralization4.5 Understanding heat of combustion4.6 Appreciating the existence of various energy sources 5. Chemicals For Consumers5.1 Analysing soap and detergent5.2 Evaluating the use of food additives5.3 Understanding Medicine5.4 Appreciating the existence of chemicals