Definition (i) Elements
- Contain just one sort of atoms
(ii) Compounds
- Contains atoms from two or more different elements bonded together chemically
- Properties of compound differs from its constituent elements
(iii) Mixtures
- Consists of more than one element or compound mixed but chemically uncombined
(iv) Mole
- Defined as the amount of a substance that contains the same amount of entities as there are atoms in exactly 12.0g of carbon-12
- Avogadro's constant, 6.02 X 10^23
Relative Atomic, Isotopic, Molecular and Formula Masses Relative Atomic Mass
- Average mass of one atom of the element / (1/12 the mass of carbon-12)
Relative Isotopic Mass
- Mass of one atom of an isotope of an element / (1/12 the mass of carbon-12)
Relationship between Relative Atomic Mass and Relative Isotopic Mass
- Relative Atomic Mass = Sum of ( Relative abundance X Relative Isotopic Mass)
Relative Molecular Mass
- Relative Molecular Mass = Sum of ( Relative Atomic Mass X All Atoms in Molecular Formula)
Relative Formula Mass
- Relative Formula Mass = Sum of ( Relative Atomic Mass X All Atoms in Formula unit)
Relative Masses, Moles and Number of Chemical Entities
- Number of moles of substance = Mass of substance / Molar Mass of substance
- Number of chemical entities = Number of Moles X 6.02 x 10^23
Chemical Formula Empirical Formula
- Simplest whole-number ratio of moles of each element in the compound
Molecular Formula
- Actual number of moles of each element in 1 mole of compound
Determination of Chemical Formula
(i) Composition of Mass
(i) Elements
- Contain just one sort of atoms
(ii) Compounds
- Contains atoms from two or more different elements bonded together chemically
- Properties of compound differs from its constituent elements
(iii) Mixtures
- Consists of more than one element or compound mixed but chemically uncombined
(iv) Mole
- Defined as the amount of a substance that contains the same amount of entities as there are atoms in exactly 12.0g of carbon-12
- Avogadro's constant, 6.02 X 10^23
Relative Atomic, Isotopic, Molecular and Formula Masses
Relative Atomic Mass
- Average mass of one atom of the element / (1/12 the mass of carbon-12)
Relative Isotopic Mass
- Mass of one atom of an isotope of an element / (1/12 the mass of carbon-12)
Relationship between Relative Atomic Mass and Relative Isotopic Mass
- Relative Atomic Mass = Sum of ( Relative abundance X Relative Isotopic Mass)
Relative Molecular Mass
- Relative Molecular Mass = Sum of ( Relative Atomic Mass X All Atoms in Molecular Formula)
Relative Formula Mass
- Relative Formula Mass = Sum of ( Relative Atomic Mass X All Atoms in Formula unit)
Relative Masses, Moles and Number of Chemical Entities
- Number of moles of substance = Mass of substance / Molar Mass of substance
- Number of chemical entities = Number of Moles X 6.02 x 10^23
Chemical Formula
Empirical Formula
- Simplest whole-number ratio of moles of each element in the compound
Molecular Formula
- Actual number of moles of each element in 1 mole of compound
Determination of Chemical Formula
(i) Composition of Mass
(ii) Combustion Analysis
Concentrations
- Concentration = Amount of moles / Molar volume
- C2 = C1 ( V1 / V2)
Stochiometry
Important notes
- Limiting reagent
- Molar volume of any gas:
(r.t.p) 25 degrees = 24.0 dm^3 / mol
(s.t.p) 22.5 degrees = 22.4 dm^3 / mol
Titration
- Indicators:
Redox Reaction
Oxidation
- Process where substances lose an electron
- Increase in oxidation state of an atom
Reduction
- Process where substances gain an electron
- Decrease in oxidation state of an atom
Oxidising Agent
- One which undergoes reduction and in process oxidises another substance
- Examples:
Alkaline
MnO2
Purple
Reducing Agent
- One which undergoes oxidation and in process reduces another substance
- Examples:
Special Cases
I2 + 2 S2O32- --> 2 I- + 2 S4O62-
IO3- + 6H+ + 5I- à 3I2 + 3H2O