Specification Point 1.27:
Know that the Mole (mol) is the unit for the amount of a substance
What is the Mole?
Mole: The mass of substance containing the same number of fundamental units as there are atoms in exactly 12.000 g of 12C. Mole is the unit representing the amount of atoms, ions, or molecules.
- One Mole is the amount of a substance that contains 6 x 1023 particles (Atoms, Molecules or Formulae) of the substance (6 x 1023 is known as the Avogadro Number).
1 mole of Sodium (Na) contains 6 x 1023 Atoms of Sodium
1 mole of Hydrogen (H2) contains 6 x 1023 Molecules of Hydrogen
1 mole of Sodium Chloride (NaCl) contains 6 x 1023 Formulae of Sodium Chloride
Specification Point 1.28:
Understand how to carry out calculations involving amount of substance, Relative Atomic Mass (Ar) and Relative Formula Mass (Mr)
Amount in Moles = Mass of Substance in grams ÷ Mr (or Ar)
|NaOH||80 g||40||( 80 ÷ 40 ) = 2 moles|
|CaCO3||25 g||100||( 25 ÷ 100 ) = 0.25 moles|
|H2SO4||4.9 g||98||4.9 ÷ 98 ) = 0.05 moles|
|H2O||108 g||18||( 108 ÷ 18 ) = 6 moles|
|CuSO4.5H2O||75 g||250||( 75 ÷ 250 ) = 0.3 moles|
Mass of Substance (grams) = Moles x Mr
|H2O||0.5 moles||18||( 0.5 x 18 ) = 9 g|
|NaCl||3 moles||58.5||( 3 x 58.5 ) = 175.5 g|
|K2CO3||0.2 moles||138||( 0.2 x 138 ) = 27.6 g|
|(NH4)2SO4||2.5 moles||132||( 2.5 x 132 ) = 330 g|
|MgSO4.7H2O||0.25 moles||246||( 0.25 x 246 ) = 61.5 g|
CALCULATING RELATIVE FORMULA MASS
Mr = Mass of Substance in Grams ÷ Moles
10 moles of Carbon Dioxide has a Mass of 440 g. What is the Relative Formula Mass of Carbon Dioxide?
Relative Formula Mass = Mass ÷ Number of Moles
Relative Formula Mass = 440 ÷ 10 = 44
Relative Formula Mass of Carbon Dioxide = 44
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Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.
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