1502
DESCRIPTION
xxxTRANSCRIPT
ADDITIONAL SCIENCE FORM 5
CHAPTER 2: CHEMICAL REACTION
2.1 IONIC COMPOUNDS
Ionic compound is formed by the transfer of one or more electrons from the outer shell of a metal atom to the outer shell of a non-metal atom.
2.1 IONIC COMPOUNDS
Positive ion Formula Hydrogen ion H+
Lithium ion Li+
Sodium ion Na+
Potassium ion K+
Magnesium ion Mg2+
Calcium ion Ca2+
Lead (II) ion Pb2+
Copper (II) ion Cu2+
Aluminium ion Al3+
2.1 IONIC COMPOUNDS
Negative ion Formula Fluoride ion F-
Chloride ion CI-
Bromide Br-
Hydroxide ion OH-
Nitrate ion NO3-
Sulphate ion SO42-
Carbonate ion CO32-
Oxide ion O2-
2.1 IONIC COMPOUNDS
The formation of an ionic compound involves a metal atom and a non-metal atom. An ionic bond is the electrostatic force of attraction between 2 oppositely-charged ions.
2.1 IONIC COMPOUNDS
Formation of sodium chloride1. The electron configuration of sodium atom is 2.8.1. 2. Sodium atom loses one valence electron to achieve a stable octet valence electron configuration. Sodium ion, Na+ is formed. Na Na+ + e-
2.1 IONIC COMPOUNDS
3. The electron configuration of chlorine atom is 2.8.7. 4. Chlorine atom accepts the electron that is lost by sodium atom to achieve a stable octet valence electron configuration. Chloride ion, CI- is formed. CI + e- CI-
2.1 IONIC COMPOUNDS
5. The oppositely-charged ions are attracted to each other by an ionic bond. [ Na ] + [ CI ] [ Na ]+ [ CI ]-
2.1 IONIC COMPOUNDS
Formation of magnesium fluoride1. The electron configuration of magnesium atom is 2.8.2. 2. Magnesium atom loses 2 valence electrons to achieve a stable octet valence electron configuration. Magnesium ion, Mg2+ is formed. Mg Mg2+ + 2e-
2.1 IONIC COMPOUNDS
3. The electron configuration of fluorine atom is 2.7. 4. 2 fluorine atoms accept 2 electrons lost by magnesium atom to achieve stable octet valence electron configuration. 2 fluoride ions are formed. F + e- F-
2.1 IONIC COMPOUNDS
5. The oppositely-charged ions are attracted to each other by an ionic bond. [ Mg ] +2[ F ] [ Mg ] 2+ [ F ]-
2
2.1 IONIC COMPOUNDS
To determine the formula of an ionic compound, the charges of the cation and anion are interchanged. Al3+ CI-
Al Cl3
2.2 REDOX REACTION
Redox is a chemical reaction that involves both oxidation and reduction.
Oxidation Reduction In terms of oxygen
Gain of oxygen Loss of oxygen In terms of electron
Loss of electron Gain of electron
2.2 REDOX REACTION
Magnesium is oxidised to magnesium oxide because it has gained oxygen.Carbon dioxide is reduced to carbon because it has lost oxygen.
2 Mg + CO2 2MgO + C Gain of oxygen - Oxidation
Loss of oxygen – Reduction
2.2 REDOX REACTION
Magnesium is a reducing agent.Carbon dioxide is an oxidising agent.
2 Mg + CO2 2MgO + C
Magnesium is a reducing agent because it causes CO2 to be reduced to C
CO2 is an oxidising agent because it causes magnesium to be oxidised to MgO
2.2 REDOX REACTION
Sodium is said to be oxidised because sodium atom has lost one electron in its valence shell to form sodium ion.
2 Na + CI2 2NaCI Loss of electron - Oxidation
Gain of electron - Reduction
2.2 REDOX REACTION
Chlorine is said to be reduced because chlorine molecule has accepted electron in its valence shell to form chloride ion.
2.2 REDOX REACTION
A chemical cell produces electricity from a chemical reaction. It consists of 2 electrodes immersed in an electrolyte. Electrode - the substance that conduct electricity Electrolyte - solution that conducts electricity
2.2 REDOX REACTION
Chemical cell
When the needle of the voltmeter deflects to the left, this indicates that iron plate is the negative terminal and
copper plate is the positive terminal
Copper (II) ion accepts 2 electron and is reduced to copper atom
Half-cell reaction for reduction:Cu2+ + 2e- Cu
Ionic equation for the chemical cell:Fe + Cu2+ Fe2+ + Cu
2.2 REDOX REACTION
K NaCaMgAl ZnFeSn PbCu HgAg Au
Decreasing electropositivity
Easiest to lose electron
Hardest to lose electron
2.2 REDOX REACTION
Application of redox
reactions
Chemical cells- Produces
electricity from a chemical reaction
Electroplating- Coating a
metal with a less
electropositive metal
Electrochemical protection
- Preventing corrosion by attaching a
more electropositive metal to a metal that is needed to be protected
Metal extraction- Process of separating a
metal from its impurities
2.2 REDOX REACTION
Chemical cell
2.2 REDOX REACTION
Types of chemical cell Uses
Lead-acid accumulator Automobiles
Lead (IV) oxide
2.2 REDOX REACTION
Types of chemical cell Uses
Alkaline cell Camera, walkman
Manganese (IV) oxide (positive
terminal)
Separator
Electrolyte
Zinc powder (negative powder)
2.2 REDOX REACTION
Types of chemical cell Uses
Dry cell Radio, torch light
Zinc (negative terminal)
Graphite rod (positive terminal)
Electrolyte
2.2 REDOX REACTION
Types of chemical cell Uses
Mercury cell Calculator
Mercury (II) oxide (positive terminal) Zinc (negative terminal)
Electrolyte
2.2 REDOX REACTION
Types of chemical cell Uses
Nickel-cadmium cell Laptop computers, handphones
Nickel (IV) oxide (positive terminal)
Cadmium (negative terminal)
Separator
Separator