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THE MOLE 1.1.4

THE MOLE 1.1.4. Explain the terms: amount of substance; mole; and the Avogadro constant. Define and use the term molar mass. Carry out calculations involving masses using the amount of substance in moles. 2008 SPECIFICATIONS. DON’T BE LEFT IN THE DARK!. THE MOLE.

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THE MOLE 1.1.4

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  1. THE MOLE 1.1.4 • Explain the terms: amount of substance; mole; and the Avogadro constant. • Define and use the term molar mass. • Carry out calculations involving masses using the amount of substance in moles 2008 SPECIFICATIONS

  2. DON’T BE LEFT IN THE DARK! THE MOLE • Before you start it would be helpful to… • know how to balance simple equations • know how to re-arrange mathematical formulae

  3. THE MOLE WHAT IS A MOLE ? it is the standard unit of amount of a substance - it is just a number, a very big number it is a way of saying a number in words, just like... DOZEN for 12 SCORE for 20 GROSS for 144

  4. THE MOLE WHAT IS A MOLE ? it is the standard unit of amount of a substance - it is just a number, a very big number it is a way of saying a number in words, just like... DOZEN for 12 SCORE for 20 GROSS for 144 HOW BIG IS IT ? 602200000000000000000000 (Approximately)... THAT’S BIG !!! It is a lot easier to write it as...6.022 x 1023

  5. THE MOLE WHAT IS A MOLE ? it is the standard unit of amount of a substance - it is just a number, a very big number it is a way of saying a number in words, just like... DOZEN for 12 SCORE for 20 GROSS for 144 HOW BIG IS IT ? 602200000000000000000000 (Approximately)... THAT’S BIG !!! It is a lot easier to write it as...6.022 x 1023 It is also known as...AVOGADRO’S NUMBER It doesn’t matter what the number is as long as everybody sticks to the same value !

  6. THE MOLE WHY USE IT ? Atoms and molecules don’t weigh much so it is easier to count large numbers of them. In fact it is easier to weigh substances. Using moles tells you... how many particles you get in a certain mass the mass of a certain number of particles DO I NEED TO KNOW ANYTHING ELSE ? Yes, it would help if you can balance equations AND Keep trying, you will get the idea ... EVENTUALLY!

  7. THE MOLE – AN OVERVIEW WHAT IS IT?The standard unit of amount of a substance - just as the standard unit of length is a METRE It is just a number, a very big number It is also a way of saying a number in words like DOZEN for 12 GROSS for 144

  8. THE MOLE – AN OVERVIEW WHAT IS IT?The standard unit of amount of a substance - just as the standard unit of length is a METRE It is just a number, a very big number It is also a way of saying a number in words like DOZEN for 12 GROSS for 144 HOW BIG IS IT ?602200000000000000000000(approx) - THAT’S BIG !!! It is a lot easier to write it as 6.022 x 1023 And anyway it doesn’t matter what the number is as long as everybody sticks to the same value !

  9. THE MOLE – AN OVERVIEW WHAT IS IT?The standard unit of amount of a substance - just as the standard unit of length is a METRE It is just a number, a very big number It is also a way of saying a number in words like DOZEN for 12 GROSS for 144 HOW BIG IS IT ?602200000000000000000000(approx) - THAT’S BIG !!! It is a lot easier to write it as 6.022 x 1023 And anyway it doesn’t matter what the number is as long as everybody sticks to the same value ! WHY USE IT ?Atoms and molecules don’t weigh much so it is easier to count large numbers of them. In fact it is easier to weigh substances. Using moles tells you :-how many particles you get in a certain mass the mass of a certain number of particles

  10. Calculation of Molar Mass from Relative Atomic Mass data When you carry out experiments you will weigh chemicals in grams. Molar mass has the same numerical value as the . . . Relative Molecular Mass; . . . . . it is calculated by adding together the relative atomic masses of the elements in the molecule. The total is expressed in units of grams per mol or g mol-1.

  11. Example 1 Calculate the Molar Mass of sulphuric acid H2SO4 This molecule contains 2 atoms of hydrogen each of mass 1.0 2 x 1.0 = 2.0 g mol–1 1 atom of sulphur of mass 32.1 1 x 32.1 = 32.1 g mol–1 4 atoms of oxygen of mass 16.0 4 x 16.0 = 64.0 g mol–1 Total mass = 98.1 g mol–1

  12. Example 2 Calculate the Molar Mass of lead nitrate Pb(NO3)2 This molecule contains TWO nitrate groups 1 atom of lead of mass 207.2 1 x 207.2 = 207.2 g mol–1 2 atoms of nitrogen of mass 14.0 2 x 14.0 = 28.0 g mol–1 6 atoms of oxygen of mass 16.0 6 x 16.0 = 96.0 g mol–1 Total mass = 331.2 g mol–1

  13. Example 3 Calculate the Molar Mass of CuSO4.5H2O In CuSO41 atom of copper of mass 63.5 1 x 63.5 = 63.5 g mol–1 1 atom of sulphur of mass 32.1 1 x 32.1 = 32.1 g mol–1 4 atoms of oxygen of mass 16.0 4 x 16.0 = 64.0 g mol–1 In 5H2O 5 x 2 atoms of hydrogen of mass 1.0 10 x 1.0 = 10.0 g mol–1 5 x 1 atoms of oxygen of mass 16.0 5 x 16.0 = 80.0 g mol–1 Total mass = 249.6 g mol–1

  14. Exercise 1.1.4 Molar mass odds and evens . . . 3 significant figures only ! 1,3,5,7, . . . . . or 2,4,6,8, . . . . . Stop at 30 !!! Now complete 31 to 60 !! Again just do - odds and evens . . .

  15. MOLES = MASS MOLAR MASS THE MOLE CALCULATING THE NUMBER OF MOLES OF A SINGLE SUBSTANCE moles = mass / molar mass mass = moles x molar mass molar mass = mass / moles UNITS mass g or kg molar mass g mol-1or kg mol-1 MASS MOLES x MOLAR MASS COVER UP THE VALUE YOU WANT AND THE METHOD OF CALCULATION IS REVEALED

  16. MOLES = NUMBER OF PARTICLES Avogadro's number THE MOLE CALCULATING THE NUMBER OF MOLES OF A SINGLE SUBSTANCE moles = Particles / 6.02x1023 Number of Particles = moles x 6.02x1023 6.02x1023 = Particles / moles UNITS Number ? Number of Particles MOLES x NA

  17. MOLES OF A SINGLE SUBSTANCE 1. Calculate the number of moles of oxygen molecules in 4.0g

  18. MOLES OF A SINGLE SUBSTANCE 1. Calculate the number of moles of oxygen molecules in 4g oxygen molecules have the formula O2 relative mass will be 2 x 16.0 = 32.0 molar mass will be 32.0g mol-1

  19. MOLES OF A SINGLE SUBSTANCE 1. Calculate the number of moles of oxygen molecules in 4g oxygen molecules have the formula O2 relative mass will be 2 x 16 = 32 ; molar mass will be 32g mol-1 moles = mass = 4g = 0.125 mol molar mass 32g mol -1

  20. MOLES OF A SINGLE SUBSTANCE 1. Calculate the number of moles of oxygen molecules in 4g oxygen molecules have the formula O2 relative mass will be 2 x 16 = 32 ; molar mass will be 32g mol-1 moles = mass = 4.0g = 0.125 mol molar mass 32.0 g mol -1

  21. Exercise 1.1.4 a Calculate the number of moles of material in a given mass of the material Again just do - odds and evens . . . 1,3,5,7, . . . . . or 2,4,6,8, . . . . . 3 significant figures only ! Now complete 30 ! That's only 15 . . . Its easy. . . .

  22. Exercise 1.1.4 Molar mass odds and evens . . . 3 significant figures only ! 1,3,5,7, . . . . . or 2,4,6,8, . . . . . Stop at 30 !!! Now complete 31 to 36 !! Again just do - odds and evens . . .

  23. MOLES OF A SINGLE SUBSTANCE • 1. Calculate the number of moles of oxygen molecules in 4g • oxygen molecules have the formula O2 • relative mass will be 2 x 16 = 32 ; molar mass will be 32g mol-1 • moles = mass = 4g = 0.125 mol • molar mass 32g mol -1 • What is the mass of 0.25 mol of Na2CO3 ? • Relative Molecular Mass of Na2CO3 = (2x23) + 12 + (3x16) = 106 • Molar mass of Na2CO3 = 106g mol-1

  24. MOLES OF A SINGLE SUBSTANCE • 1. Calculate the number of moles of oxygen molecules in 4g • oxygen molecules have the formula O2 • relative mass will be 2 x 16 = 32 ; molar mass will be 32g mol-1 • moles = mass = 4g = 0.125 mol • molar mass 32g mol -1 • What is the mass of 0.25 mol of Na2CO3 ?

  25. MOLES OF A SINGLE SUBSTANCE • 1. Calculate the number of moles of oxygen molecules in 4g • oxygen molecules have the formula O2 • relative mass will be 2 x 16 = 32 ; molar mass will be 32g mol-1 • moles = mass = 4g = 0.125 mol • molar mass 32g mol -1 • What is the mass of 0.25 mol of Na2CO3 ? • Relative Molecular Mass of Na2CO3 = (2x23) + 12 + (3x16) = 106 • Molar mass of Na2CO3 = 106g mol-1 • mass = moles x molar mass = 0.25 x 106 =26.5g

  26. MOLES OF A SINGLE SUBSTANCE • 1. Calculate the number of moles of oxygen molecules in 4g • oxygen molecules have the formula O2 • relative mass will be 2 x 16 = 32 ; molar mass will be 32g mol-1 • moles = mass = 4g = 0.125 mol • molar mass 32g mol -1 • What is the mass of 0.25 mol of Na2CO3 ? • Relative Molecular Mass of Na2CO3 = (2x23) + 12 + (3x16) = 106 • Molar mass of Na2CO3 = 106g mol-1 • mass = moles x molar mass = 0.25 x 106 =26.5g

  27. Exercise 1.1.4 a Calculate the number of moles of material in a given mass of the material Again just do - odds and evens . . . 1,3,5,7, . . . . . or 2,4,6,8, . . . . . 3 significant figures only ! Now complete 50 ! That's only 25 . . . Its easy. . . .

  28. Exercise 1.1.4 b Calculate the mass of material in a given the number of moles of the material Again just do - odds and evens . . . 3 significant figures only ! 1,3,5,7, . . . . . or 2,4,6,8, . . . . . Now complete 50 ! Thats only 25 . . . Its getting easier. . . .

  29. Tasks • Write out these Key definitions • Amount of substance . . • The Avogadro constant . . • A mole . . . • Molar Mass, Mr • Worksheets Questions : 1, 2

  30. FeSO4·xH2O FeSO4 H2O Mass FeSO4 = H2O = Molar Mass FeSO4 = H2O = Moles FeSO4 = H2O = Molar Ratio : The formula of hydrated iron (II) sulphate is FeSO4·7H2O

  31. Mass of crucible and lid = _ _ . _ _ grms Mass of crucible and lid and FeSO4·xH2O = _ _ . _ _ grms First Heating 3a . Mass of crucible and lid and FeSO4·xH2O = _ _ . _ _ grms Second Heating 3b. Mass of crucible and lid and FeSO4·xH2O = _ _ . _ _ grms Third Heating 3c. Mass of crucible and lid and FeSO4·xH2O = _ _ . _ _ grms Calculations Mass of water = 3 – 2 = 1.52 grms Mass of FeSO4 = 3 – 1 = 1.26 grms

  32. 1.1.9 Tasks • Write out these Key definitions • Stoichiometry is . . . • Examiner tip is . . . . • Notes • Worksheets Questions : 1, 2, 3

  33. 1.1.4

  34. 1.1.4a

  35. 1.1.4b

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