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Chapter 6 – Ionic Bonding

1) Noble gases are unreactive and do not form compounds because they have octet structure
2) Metals form postively charged ions (Cations)
3) Non-Metals usually form neagtively charged ions (Anions)
4) Metals react with non-metals to form ionic compounds.
5) An ionic bond is formed when electrons are transfeered from a metallic atom to a non-metallic atom.

From : O Level Chemistry Tutor

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Chapter 7 – Covalent and Metallic Bonding

1. A covalent bonding is bond formed by sharing of electrons between atoms
2. A single covalent bond consists of one shared pair of electrons
3. A double covalent bond consists of two shared pair or electrons.
4. A molecule is formed when two or more atoms are joined together by covalent bonds.
5. In a molecule, each atom has the electronic configuration of a noble gas.

From : O Level Chemistry Tutor

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Chapter 8 – Writing Chemical Equations

3 Basic steps

Step 1 : Write down the chemical formulae of the reactants and products to get the chemical equation.

Step 2 : Check the number of atoms of each element in the formulae on both sides of the equation are balanced.

Step 3 : Add the state symbols

From : O Level Chemistry Tutor

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Chapter 9 – The Mole

1. A mole of any substance contains 6 x 10 power 23 particles. This number is called Avogadro’s constant

2. Number of mole of atoms = mass of the element(g)/Ar

3. Number of mole of substance = Mass of the substance(g)/Mr

4. Molar mass refer to the mass of one mole of the substance.

From : O Level Chemistry Tutor

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Chapter 10 – Chemical Calculations

What does an equation tell us?

A balanced chemical equation shows important facts about a reaction
a) The reactants
b) The products
c) The ratio of the amounts (in moles) of the reactants and the products
d) The state of each reactants/products if indicated

It is the relationship between the amounts (measured in moles) of reactants and products involved in a chemical reaction.

Exam based questions will be discussed in the lessons

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Chapter 11 – Salt

Key ideas

1. Soluble salts are prepared by the following methods:
a) Acid + a metal (excluding potassium, sodium, calcium, copper and silver)
b) Acid + an insoluble base
c) Acid + an insoluble carbonate
d) Acid + an alkali (titration method)

2. Insoluble salts are prepared by the precipitation reaction of two soluble salt solutions

O level Chemistry Tuition Tutor

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Chapter 12 – Acids and Bases

Q: What is an acid?
A: An acid is a substance which produces hydrogen ions, H+, when it is dissolved in water.

Q: What are the physical properties of acids?
A: 1. Acids have a sour taste.
2. Acids dissolve in water to form solutions which conduct electricity.
3. Acids turn blue litmus paper red.

Q: What are the chemical properties of acids?
A: 1. Acids react with reactive metals to form hydrogen gas and a salt.
metal + acid —–> salt + hydrogen

2. Acids react with carbonates to form a salt, carbon dioxide and water.
carbonate + acid —–> salt + water + carbon dioxide

3. Acids react with metal oxides and hydroxides to form a salt and water only.
metal oxide + acid —–> salt + water

metal hydroxide + acid  salt + water

Q: Do all metals react with acid?
A: No, When unreactive metals such as copper or silver are added to dilute acids, there is no reaction.

Contact Mr Ong @9863 9633 for much key ideas on acids and bases

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The Mole – Key Points

1. Both relative atomic mass and relative molecular mass have no units.

2. Empirical formula an molecular formula may or may not be the same.

3. The total percentage composition of the elements in the compound must be 100%.

4. 1 dm^3 = 1000 cm^3

5. When calculating the Mr of a substance in the reaction, do not include the coefficient.

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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Chemical Calculations – Key Points

1. Spectator ions are ions that are not involved in a chemical reaction.

2. Stoichiometetry of the reaction is the relationship between the amounts of reactants and products involved in a chemical reaction.

3. Limiting reactant is the reactant that is completely used up in a reaction and determines the amount of products formed.

4. The concentration of a solution is given by the amount of a solute dissolved in a unit volume of the solution.

5. Molar concentration is the concentration of a solution expressed in mold/dm^3

6. The theoretical yield is the calculated amount of products that would be obtained if the reaction is completed.

7. Actual yield is the amount of pure products that is actually prodcued in the experiment.

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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Acids and Bases – Key Points

1. An acid is a substance that produces hydrogen ions, H+, when dissolved in water.

2. The strength of an acid refers to the extent to which the acid molecules dissociates when dissolved in water.

3. A base is a substance that reacts with an acid to form a salt and water only.

4. An alkali is a base that is soluble in water.

5. Neutralisation reaction is the reaction between an acid and a base to from a salt and water only.

6. The term concentration tells us how much a substance is dissolved in 1 dm^3

7. The term strength refers to how an acid or an alkali dissociates when dissolved in water.

8. The pH scale is a set is a set of numbers used to whether a solution is acidic, neutral or alkaline.

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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Salt Preparation

Preparation of salt by reaction between acid and an insoluble base.

Example: Preparation of copper(II) sulfate from copper(II) oxide(insoluble base)

Step 1: Put sulfuric acid in a beaker.

Step 2: Add copper(II) oxide until no more can dissolve.
Copper(II) sulfate solution & unreacted copper(II) oxide

Step 3: Filter to remove the excess copper(II) oxide

Step 4: Collect the filtrate.

Step 5: Heat up the filtrate to evaporate the water to about 1/3 the original volume.

Step 6; Allow the filtrate to cool to room temperature so that copper(II) sulfate crystals.

Step 7: Wash the crystal with a little cold distilled water.

Step 8: Dry the crystal with filter paper

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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Oxidation and Reduction

Oxidation
– Gain of oxygen
– Gain of oxidation number
– loss of hydrogen
– loss of electron

Reduction
– loss of oxygen
– loss of oxidation number
– Gain of hydrogen
– Gain of electron

1. A redox reaction is a reaction involving oxidation and reduction.

2. An oxidising agent is a substance that causes oxidation on another substance.

3. An reducing agent is a substance that causes reduction on another substance.

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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Metals

Important Definitions

1. An alloy is a mixture of metal with one or a few other elements.

2. The reactivity series is a series of metals arranged in the order of their chemical reactivity, from the most reactivity to the lease reactivity.

3. Displacement reaction of metals is a redox reaction in which a more reactive metal displaces a less reactive metal to form its salt solution.

4. Galvanising is the coating of iron or steel on zinc for protection against corrosion.

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Electrolysis

Important Definitions

1. An electrolytic cell is a set of apparatus that uses electrical energy to produce chemical reactions.

2. Electrolysis is the process of decomposition of a compound by electricity.

3. The anode is the positive electrode and the cathode is the negative electrode of an electrolytic.

4. An electrolyte is a substance that conducts electricity in the molten state or in aqueous solution.

5. Cations are positive ions and anions are negative ions

6. The discharge of ions is the process of gaining or losing electrons at the electrode.

7. An Inert electrode is an electrode that does not take part in chemical reaction during electrolysis.

8. A reactive electrode is an electrode that participates in chemical reactions during electrolysis.

9. Electroplating is the process of coating an object with a thin layer of metal using electrolysis.

10. A simple cell is a devise that uses chemical reactions to produce electricity.

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The Periodic Tables

Important Definitions

1. A group is a vertical column of elements in the Periodic Table.

2. A period is a horizontal row of elements in the Periodic Table.

3. A metalloid is an element that has the properties of both a metal and a non-metal

4. An alkali metals are the Group I elements.

5. The halogens are the Group VII elements.

6. The noble gases are the Group 0 or Group VIII elements.

7. The transition elements are a block metallic elements between Group II and II in the Periodic table.

8. A catalyst is a substance that increases the speed of chemical reaction.

For more key points and exam based questions with full worked solutions please contact Mr Ong @98639833

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