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CALCULATIONS INVOLVING FORMULAE A guide for GCSE students

CALCULATIONS INVOLVING FORMULAE A guide for GCSE students. 2010 SPECIFICATIONS. KNOCKHARDY PUBLISHING. HOPTON. CALCULATIONS INVOLVING FORMULAE. INTRODUCTION

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CALCULATIONS INVOLVING FORMULAE A guide for GCSE students

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  1. CALCULATIONS INVOLVING FORMULAE A guide for GCSE students 2010 SPECIFICATIONS KNOCKHARDY PUBLISHING

  2. HOPTON CALCULATIONS INVOLVING FORMULAE INTRODUCTION This Powerpoint show is one of several produced to help students understand selected GCSE Chemistry topics. It is based on the requirements of the AQA specification but is suitable for other examination boards. Individual students may use the material at home for revision purposes and it can also prove useful for classroom teaching with an interactive white board. Accompanying notes on this, and the full range of AS and A2 Chemistry topics, are available from the KNOCKHARDY WEBSITE at... www.knockhardy.org.uk All diagrams, photographs and any animations in this Powerpoint are original and created by Jonathan Hopton. Permission must be obtained for their use in any work that is distributed for financial gain.

  3. HOPTON CALCULATIONS INVOLVING FORMULAE • CONTENTS • Working out simple formulae • Relative formula mass • Percentage composition • Reacting masses • Yield and percentage yield

  4. HOPTON SOME COMMON FORMULAE chlorine gas Cl2 hydrogen gas H2 nitrogen gas N2 oxygen gas O2 hydrochloric acid HCl nitric acid HNO3 sulphuric acid H2SO4 sodium hydroxide NaOH sodium chloride NaCl sodium carbonate Na2CO3 potassium chloride KCl magnesium oxide MgO magnesium hydroxide Mg(OH)2 magnesium carbonate MgCO3 magnesium sulphate MgSO4 calcium carbonate CaCO3 calcium chloride CaCl2 Many formulae can be worked out by reference to a table of ions. Others just have to be known off by heart.

  5. HOPTON TABLE OF IONS hydrogen H+ chloride Cl¯ sodium Na+ bromide Br¯ potassium K+ iodide I¯ lithium Li+ hydroxide OH¯ rubidium Rb+ nitrate NO3¯ caesium Cs+ nitrite NO2¯ silver(I) Ag+ hydrogencarbonate HCO3¯ ammonium NH4+ hydrogensulphate HSO4¯ calcium Ca2+ sulphate SO42- barium Ba2+ sulphite SO32- magnesium Mg2+ sulphide S2- zinc Zn2+ oxide O2- iron(II) “ferrous” Fe2+ carbonate CO32- copper(II) Cu2+ aluminium Al3+ iron(III) “ferric” Fe3+

  6. NUMBER OF ELECTRONS IN OUTER SHELL OF ATOMS 1 2 3 6 7 HOPTON TABLE OF IONS hydrogen H+ chloride Cl¯ sodium Na+ bromide Br¯ potassium K+ iodide I¯ lithium Li+ hydroxide OH¯ rubidium Rb+ nitrate NO3¯ caesium Cs+ nitrite NO2¯ silver(I) Ag+ hydrogencarbonate HCO3¯ ammonium NH4+ hydrogensulphate HSO4¯ calcium Ca2+ sulphate SO42- barium Ba2+ sulphite SO32- magnesium Mg2+ sulphide S2- zinc Zn2+ oxide O2- iron(II) “ferrous” Fe2+ carbonate CO32- copper(II) Cu2+ aluminium Al3+ iron(III) “ferric” Fe3+

  7. HOPTON TABLE OF IONS hydrogen H+ chloride Cl¯ sodium Na+ bromide Br¯ potassium K+ iodide I¯ lithium Li+ hydroxide OH¯ rubidium Rb+ nitrate NO3¯ caesium Cs+ nitrite NO2¯ silver(I) Ag+ hydrogencarbonate HCO3¯ ammonium NH4+ hydrogensulphate HSO4¯ calcium Ca2+ sulphate SO42- barium Ba2+ sulphite SO32- magnesium Mg2+ sulphide S2- zinc Zn2+ oxide O2- iron(II) “ferrous” Fe2+ carbonate CO32- copper(II) Cu2+ aluminium Al3+ iron(III) “ferric” Fe3+ Formulae can be worked out by balancing the charges so that… negative charge = positive charge

  8. HOPTON CONSTRUCTING FORMULAE

  9. HOPTON CONSTRUCTING FORMULAE Many formulae can be worked out by balancing the charges so that… negative charge = positive charge

  10. HOPTON CONSTRUCTING FORMULAE Q.1 Write out the correct formula for each of the following compounds. a) sodium chloride b) magnesium sulphate c) potassium oxide d) calcium chloride e) copper(II) nitrate sodium ionNa+ chloride ionCl¯

  11. Na+ Cl¯ HOPTON CONSTRUCTING FORMULAE Q.1 Write out the correct formula for each of the following compounds. a) sodium chloride b) magnesium sulphate c) potassium oxide d) calcium chloride e) copper(II) nitrate sodium ionNa+ chloride ionCl¯

  12. Na+ Cl¯ HOPTON CONSTRUCTING FORMULAE Q.1 Write out the correct formula for each of the following compounds. a) sodium chloride b) magnesium sulphate c) potassium oxide d) calcium chloride e) copper(II) nitrate sodium ionNa+ chloride ionCl¯ ONE Na+balances ONE Cl¯ FORMULA is NaCl

  13. HOPTON CONSTRUCTING FORMULAE Q.2 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate c) potassium oxide d) calcium chloride e) copper(II) nitrate magnesium ionMg2+ sulphate ionSO42- Mg2+ SO42-

  14. HOPTON CONSTRUCTING FORMULAE Q.2 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate c) potassium oxide d) calcium chloride e) copper(II) nitrate magnesium ionMg2+ sulphate ionSO42- Mg2+ SO42- ONE Mg2+ balances ONE SO42- FORMULA is MgSO4

  15. HOPTON CONSTRUCTING FORMULAE Q.3 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate MgSO4 c) potassium oxide d) calcium chloride e) copper(II) nitrate K+ potassium ionK+ oxide ionO2- K+ O2-

  16. HOPTON CONSTRUCTING FORMULAE Q.3 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate MgSO4 c) potassium oxide d) calcium chloride e) copper(II) nitrate K+ potassium ionK+ oxide ionO2- K+ O2- TWO K+ balance ONE O2- FORMULA is K2O

  17. HOPTON CONSTRUCTING FORMULAE Q.4 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate MgSO4 c) potassium oxide K2O d) calcium chloride e) copper(II) nitrate Cl¯ calcium ionCa2+ chloride ionCl¯ Ca2+ Cl¯

  18. HOPTON CONSTRUCTING FORMULAE Q.4 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate MgSO4 c) potassium oxide K2O d) calcium chloride e) copper(II) nitrate Cl¯ calcium ionCa2+ chloride ionCl¯ Ca2+ Cl¯ ONE Ca2+ balances TWOCl¯ FORMULA is CaCl2

  19. HOPTON CONSTRUCTING FORMULAE Q.5 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate MgSO4 c) potassium oxide K2O d) calcium chloride CaCl2 e) copper(II) nitrate NO3¯ copper(II) ionCu2+ nitrate ionNO3¯ Cu2+ NO3¯

  20. HOPTON CONSTRUCTING FORMULAE Q.5 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate MgSO4 c) potassium oxide K2O d) calcium chloride CaCl2 e) copper(II) nitrate NO3¯ copper(II) ionCu2+ nitrate ionNO3¯ Cu2+ NO3¯ ONE Cu2+ balances TWONO3¯ FORMULA is Cu(NO3)2

  21. HOPTON CONSTRUCTING FORMULAE Q.5 Write out the correct formula for each of the following compounds. a) sodium chloride NaCl b) magnesium sulphate MgSO4 c) potassium oxide K2O d) calcium chloride CaCl2 e) copper(II) nitrate NO3¯ copper(II) ionCu2+ nitrate ionNO3¯ Cu2+ NO3¯ NOTE THE BRACKETS If the brackets weren’t there, the formula would appear as CuNO32 (thirty two oxygens). Brackets are used when the ion has more than one element in it. eg NO3¯ OH¯ NH4+ ONE Cu2+ balances TWONO3¯ FORMULA is Cu(NO3)2

  22. HOPTON FORMULAE – Test questions Write out the correct formula for each of the following compounds. a) lithium chlorideLiCl b) calcium sulphateCaSO4 c) sodium oxideNa2O d) calcium chlorideCaCl2 e) iron(II) nitrateFe(NO3)2 f) potassium sulphateK2SO4 g) calcium hydroxideCa(OH)2 h) zinc carbonateZnCO3 i) aluminium oxideAl2O3 j) aluminium sulphateAl2(SO4)3 k) ammonium nitrateNH4NO3 l) ammonium chlorideNH4Cl m) ammonium sulphate(NH4)2SO4 n) iron(III) chloride FeCl3

  23. HOPTON FORMULAE – Test questions Write out the correct formula for each of the following compounds. a) lithium chlorideLiCl b) calcium sulphateCaSO4 c) sodium oxideNa2O d) calcium chlorideCaCl2 e) iron(II) nitrateFe(NO3)2 f) potassium sulphateK2SO4 g) calcium hydroxideCa(OH)2 h) zinc carbonateZnCO3 i) aluminium oxideAl2O3 j) aluminium sulphateAl2(SO4)3 k) ammonium nitrateNH4NO3 l) ammonium chlorideNH4Cl m) ammonium sulphate(NH4)2SO4 n) iron(III) chloride FeCl3

  24. HOPTON RELATIVE FORMULA MASS

  25. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relativeatomic masses of ALL the atoms present in the formula

  26. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relativeatomic masses of ALL the atoms present in the formula To calculate this value, it is important that one understands how to work out the number of each type of atom present.

  27. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relativeatomic masses of ALL the atoms present in the formula To calculate this value, it is important that one understands how to work out the number of each type of atom present. A small subscript number tells you how many there of the atom just before the subscript

  28. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relativeatomic masses of ALL the atoms present in the formula To calculate this value, it is important that one understands how to work out the number of each type of atom present. A small subscript number tells you how many there of the atom just before the subscript H2O2 hydrogen atoms 1 oxygen atom (a 1 after the O is unnecessary)

  29. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relativeatomic masses of ALL the atoms present in the formula To calculate this value, it is important that one understands how to work out the number of each type of atom present. A small subscript number tells you how many there of the atom just before the subscript H2O 2 hydrogen atoms 1 oxygen atom (a 1 after the O is unnecessary) Ca(OH)21 calcium atom 2 lots of everything in the bracket ie 2 oxygen atoms and 2 hydrogen atoms (groups of atoms occurring in brackets include… SO4 NO3 NH4 OH)

  30. HOPTON RELATIVE FORMULA MASS HOW MANY ATOMS OF EACH TYPE ARE IN THE FOLLOWING? a) H2O 2 x H 1 x O b) NaOH 1 x Na 1 x O 1 x H c) (NH4)2SO4 2 x N 4 x O 8 x H 1 x S d) Ca(OH)2 1 x Ca 2 x O 2 x H e) H2SO4 2 x H 4 x O 1 x S f) CuSO4.5H2O 1 x Cu 10 x H 9 x O 1 x S

  31. HOPTON RELATIVE FORMULA MASS HOW MANY ATOMS OF EACH TYPE ARE IN THE FOLLOWING? a) H2O 2 x H 1 x O b) NaOH 1 x Na 1 x O 1 x H c) (NH4)2SO4 2 x N 4 x O 8 x H 1 x S d) Ca(OH)2 1 x Ca 2 x O 2 x H e) H2SO4 2 x H 4 x O 1 x S f) CuSO4.5H2O 1 x Cu 10 x H 9 x O 1 x S

  32. HOPTON RELATIVE FORMULA MASS HOW MANY ATOMS OF EACH TYPE ARE IN THE FOLLOWING? a) H2O 2 x H 1 x O b) NaOH 1 x Na 1 x O 1 x H c) (NH4)2SO4 2 x N 4 x O 8 x H 1 x S d) Ca(OH)2 1 x Ca 2 x O 2 x H e) H2SO4 2 x H 4 x O 1 x S f) CuSO4.5H2O 1 x Cu 10 x H 9 x O 1 x S A NUMBER IN THE FRONT OF A FORMULA MULTIPLIES EVERYTHING IN THAT FORMULA

  33. HOPTON RELATIVE FORMULA MASS HOW MANY ATOMS OF EACH TYPE ARE IN THE FOLLOWING? a) H2O 2 x H 1 x O b) NaOH 1 x Na 1 x O 1 x H c) (NH4)2SO4 2 x N 4 x O 8 x H 1 x S d) Ca(OH)2 1 x Ca 2 x O 2 x H e) H2SO4 2 x H 4 x O 1 x S f) CuSO4.5H2O 1 x Cu 10 x H 9 x O 1 x S A NUMBER IN THE FRONT OF A FORMULA MULTIPLIES EVERYTHING IN THAT FORMULA g) 2 NaOH 2 x Na 2 x O 2 x H h) 3 Ca(OH)2 3 x Ca 6 x O 6 x H i) 2 Na2HPO4 4 x Na 8 x O 2 x H 2 x P

  34. HOPTON RELATIVE FORMULA MASS HOW MANY ATOMS OF EACH TYPE ARE IN THE FOLLOWING? a) H2O 2 x H 1 x O b) NaOH 1 x Na 1 x O 1 x H c) (NH4)2SO4 2 x N 4 x O 8 x H 1 x S d) Ca(OH)2 1 x Ca 2 x O 2 x H e) H2SO4 2 x H 4 x O 1 x S f) CuSO4.5H2O 1 x Cu 10 x H 9 x O 1 x S A NUMBER IN THE FRONT OF A FORMULA MULTIPLIES EVERYTHING IN THAT FORMULA g) 2 NaOH 2 x Na 2 x O 2 x H h) 3 Ca(OH)2 3 x Ca 6 x O 6 x H i) 2 Na2HPO4 4 x Na 8 x O 2 x H 2 x P

  35. HOPTON HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula

  36. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula WaterH2O H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  37. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula WaterH2OH + H + O H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  38. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula WaterH2O H + H + O 1 + 1 + 16 = 18 H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  39. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 CopperCuSO4 sulphate H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  40. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 CopperCuSO4Cu + S + 4 x O sulphate H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  41. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 CopperCuSO4Cu + S + 4 x O sulphate64 + 32 + 4 x 16 H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  42. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 CopperCuSO4Cu + S + 4 x O sulphate64 + 32 + 4 x 16 =160 H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  43. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 Copper CuSO4 Cu + S + 4 x O sulphate 64 + 32 + 4 x 16 = 160 TAKE CARE WHEN THERE ARE BRACKETS H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  44. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 Copper CuSO4 Cu + S + 4 x O sulphate 64 + 32 + 4 x 16 = 160 TAKE CARE WHEN THERE ARE BRACKETS CalciumCa(OH)2 hydroxide H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  45. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 Copper CuSO4 Cu + S + 4 x O sulphate 64 + 32 + 4 x 16 = 160 TAKE CARE WHEN THERE ARE BRACKETS CalciumCa(OH)2Ca + 2 lots of OH hydroxide H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  46. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 Copper CuSO4 Cu + S + 4 x O sulphate 64 + 32 + 4 x 16 = 160 TAKE CARE WHEN THERE ARE BRACKETS CalciumCa(OH)2Ca + 2 lots of OH hydroxideCa + O + H + O + H H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  47. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 Copper CuSO4 Cu + S + 4 x O sulphate 64 + 32 + 4 x 16 = 160 TAKE CARE WHEN THERE ARE BRACKETS CalciumCa(OH)2Ca + 2 lots of OH hydroxideCa + O + H + O + H 40 16 + 1 + 16 + 1 H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  48. HOPTON RELATIVE FORMULA MASS The relative formula mass is the sum of the relative atomic masses of ALL the atoms present in the formula Water H2O H + H + O 1 + 1 + 16 = 18 Copper CuSO4 Cu + S + 4 x O sulphate 64 + 32 + 4 x 16 = 160 TAKE CARE WHEN THERE ARE BRACKETS CalciumCa(OH)2Ca + 2 lots of OH hydroxideCa + O + H + O + H 40 16 + 1 + 16 + 1=74 H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  49. HOPTON RELATIVE FORMULA MASS Use the list of relative atomic masses to calculate the relative formula mass of the following compounds H2 O2 H2O NaOH CH4 C5H12 NaCl H2SO4 Na2SO4 CaCl2 CaCO3 NH4NO3 CuSO4 Al2O3 Ca(OH)2 Al2(SO4)3 H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

  50. HOPTON RELATIVE FORMULA MASS Use the list of relative atomic masses to calculate the relative formula mass of the following compounds H2 O2 H2O NaOH CH4 C5H12 NaCl H2SO4 Na2SO4 CaCl2 CaCO3 NH4NO3 CuSO4 Al2O3 Ca(OH)2 Al2(SO4)3 2 32 18 40 16 72 36.5 98 142 111 100 80 160 102 74 342 H = 1; C = 12; N = 14; O = 16; Na = 23; Mg = 24; Al = 27; S = 32; Cl = 35.5; K = 39; Ca = 40; Fe = 56; Cu = 64

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