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Empirical Formula The empirical formula gives the simplest whole number ratio of each type of atom in a compound e.g. The molecular formula of butane is.

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Presentation on theme: "Empirical Formula The empirical formula gives the simplest whole number ratio of each type of atom in a compound e.g. The molecular formula of butane is."— Presentation transcript:

1 Empirical Formula The empirical formula gives the simplest whole number ratio of each type of atom in a compound e.g. The molecular formula of butane is C 4 H 10 The empirical formula of butane is C 2 H 5 Molecular Formula A molecular formula shows the elements that a compound is made out of and the number of atoms of each element present in one molecule of the compound. The numbers are shown written as subscripts. e.g. The molecular formula of butane is C 4 H 10 One molecule of ethane contains 4 carbon atoms and 10 hydrogen atoms. The molecular formula of water is H 2 O One molecule of water contains 2 hydrogen atoms and one oxygen atom.

2 ElementSymbolRelative Atomic Mass Hydrogen H1 Carbon C12 Oxygen O16 Nitrogen N14 Calcium Ca40 Silicon Si28 Relative molecular mass Molecules are incredibly light so when discussing how heavy a molecule is Chemists often find the relative molecular mass. This is measured in atomic mass units. The table below shows the relative atomic masses of various elements which can be used to calculate the relative molecular mass of molecules. e.g. The molecular formula of butane is C 4 H 10 The relative molecular mass of ethane is 4 x 12 + 10 x 1 = 58 atomic mass units

3 Elemental Analysis Is a technique that allows a chemist to workout (as a percentage) how much each element contributes to the total mass of the molecule. If you know these percentages you can work out what the empirical formula of a molecule so it can help Chemists work out what they have made. Ratio Percentages Fractions Substitution

4 ElementSymbol Relative Atomic Mass Hydrogen H 1 Carbon C 12 Oxygen O 16 Nitrogen N 14 Calcium Ca 40 Silicon Si 28 Use your skills with fractions, percentages, ratios and substitution to work out missing information about molecules and even identify mystery compounds. Use the table below to help you.

5 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 3:6 CH 2 1:212:2 C: 85.7% H: 14.3%42 C 12 H 18 C 6 H 12 O 6 C6H6C6H6 CaCO 3 SiH 4

6 There a few different ways of using this resource: 1.Fill in the gaps in the table (possibly in pairs- each use a different colour) 2. Cut up the completed grid and use it as a card sort (possibly only use one slide rather than two) 3.Print the reversed complete grid with a picture on the back of the page before you cut it out into cards. Put the cards in the correct places on the template grid. Flip over each card to reveal the picture (and hence check the cards are in the correct place.

7 Fill in gaps (given formula)

8 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 C 12 H 18 C 6 H 12 O 6 C6H6C6H6 CaCO 3 SiH 4

9 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) CH 4 N 60 CH 4 16 CH 3 O 62 CH 3 30 C5H4C5H4 128 CHO 2 90

10 answers

11 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 3:6 CH 2 1:212:2 C: 85.7% H: 14.3%42 C 12 H 18 12:18 C2H3C2H3 2:324:3 C: 88.9% H: 11.1%162 C 6 H 12 O 6 6:12:6 CH 2 O 1:2:112:2:16 C:40% H 6.7% O: 53.3% 180 C6H6C6H6 6:6 CH 1:112:1 C: 92.3% H: 7.7%78 CaCO 3 1:1:3 CaCO 3 1:1:340:12:48 Ca: 40% C: 12% O: 48% 100 SiH 4 1:4 SiH 4 1:428:4 Si: 87.5% H: 12.5%32

12 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C2H8N2C2H8N2 2:6:2 CH 4 N 1:4:112:4:14 C:40% H: 13.3% N: 46.7% 60 CH 4 1:4 CH 4 1:412:4 C: 75% H: 25%16 C2H6O2C2H6O2 2:6:2 CH 3 O 1:3:112:3:16 C: 38.7% H: 9.7% O: 51.6% 62 C2H6C2H6 2:6 CH 3 1:312:3 C: 80% H: 20%30 C 10 H 8 10:8 C5H4C5H4 5:460:4 C: 93.75% H: 6.25%128 C2H2O4C2H2O4 2:2:4 CHO 2 1:1:212:1:32 C: 26.7% H: 2.2% O: 71.1% 90

13 Fill in gaps (harder)

14 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 C 12 H 18 CH 2 O 180 C:H 78 Ca: 40% C: 12% O: 48% 100 SiH 4 32

15 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C:H:N 60 C: 75% H: 25%16 C:H:O 12:3:1662 C: 80% H: 20%30 C: 93.75% H: 6.25%128 C: 26.7% H: 2.2% O: 71.1% 90

16 answers

17 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 3:6 CH 2 1:212:2 6:1 C: 85.7% H: 14.3%42 C 12 H 18 12:18 C2H3C2H3 2:324:3 8:1 C: 88.9% H: 11.1%162 C 6 H 12 O 6 6:12:6 CH 2 O 1:2:112:2:16 6:1:8 C:40% H 6.7% O: 53.3% 180 C6H6C6H6 6:6 CH 1:112:1 C: 92.3% H: 7.7%78 CaCO 3 1:1:3 CaCO 3 1:1:340:12:48 10:3:12 Ca: 40% C: 12% O: 48% 100 SiH 4 1:4 SiH 4 1:428:4 7:1 Si: 87.5% H: 12.5%32

18 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C2H8N2C2H8N2 2:6:2 CH 4 N 1:4:112:4:14 6:2:7 C:40% H: 13.3% N: 46.7% 60 CH 4 1:4 CH 4 1:412:4 3:1 C: 75% H: 25%16 C2H6O2C2H6O2 2:6:2 CH 3 O 1:3:112:3:16 C: 38.7% H: 9.7% O: 51.6% 62 C2H6C2H6 2:6 CH 3 1:312:3 4:1 C: 80% H: 20%30 C 10 H 8 10:8 C5H4C5H4 5:460:4 15:1 C: 93.75% H: 6.25%128 C2H2O4C2H2O4 2:2:4 CHO 2 1:1:212:1:32 C: 26.7% H: 2.2% O: 71.1% 90

19 Card sort

20 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 3:6 CH 2 1:212:2 6:1 C: 85.7% H: 14.3%42 C 12 H 18 12:18 C2H3C2H3 2:324:3 8:1 C: 88.9% H: 11.1%162 C 6 H 12 O 6 6:12:6 CH 2 O 1:2:112:2:16 6:1:8 C:40% H 6.7% O: 53.3% 180 C6H6C6H6 6:6 CH 1:112:1 C: 92.3% H: 7.7%78 CaCO 3 1:1:3 CaCO 3 1:1:340:12:48 10:3:12 Ca: 40% C: 12% O: 48% 100 SiH 4 1:4 SiH 4 1:428:4 7:1 Si: 87.5% H: 12.5%32

21 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C2H8N2C2H8N2 2:6:2 CH 4 N 1:4:112:4:14 6:2:7 C:40% H: 13.3% N: 46.7% 60 CH 4 1:4 CH 4 1:412:4 3:1 C: 75% H: 25%16 C2H6O2C2H6O2 2:6:2 CH 3 O 1:3:112:3:16 C: 38.7% H: 9.7% O: 51.6% 62 C2H6C2H6 2:6 CH 3 1:312:3 4:1 C: 80% H: 20%30 C 10 H 8 10:8 C5H4C5H4 5:460:4 15:1 C: 93.75% H: 6.25%128 C2H2O4C2H2O4 2:2:4 CHO 2 1:1:212:1:32 C: 26.7% H: 2.2% O: 71.1% 90

22 Card sort with template (given formula)

23 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 C 12 H 18 C 6 H 12 O 6 C6H6C6H6 CaCO 3 SiH 4

24 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C2H8N2C2H8N2 CH 4 C2H6O2C2H6O2 C2H6C2H6 C 10 H 8 C2H2O4C2H2O4

25 Relative molecular mass (amu) % by massFraction of total mass for each element Ratio of masses Simplified Ratio Empirical formula RatioMolecular Formula 42 C: 85.7% H: 14.3%12:2 6:1 1:2 CH 2 3:6 C3H6C3H6 162 C: 88.9% H: 11.1%24:3 8:1 2:3 C2H3C2H3 12:18 C 12 H 18 180 C:40% H 6.7% O: 53.3% 12:2:16 6:1:8 1:2:1 CH 2 O 6:12:6 C 6 H 12 O 6 78 C: 92.3% H: 7.7%12:11:1 CH 6:6 C6H6C6H6 100 Ca: 40% C: 12% O: 48% 40:12:48 10:3:12 1:1:3 CaCO 3 1:1:3 CaCO 3 32 Si: 87.5% H: 12.5%28:4 7:1 1:4 SiH 4 1:4 SiH 4

26 (insert picture of your own choice)

27 Relative molecular mass (amu) % by massFraction of total mass for each element Ratio of masses Simplified Ratio Empirical formula RatioMolecular Formula 60 C:40% H: 13.3% N: 46.7% 12:4:14 6:2:7 1:4:1 CH 4 N 2:6:2 C2H8N2C2H8N2 16 C: 75% H: 25%12:4 3:1 1:4 CH 4 1:4 CH 4 62 C: 38.7% H: 9.7% O: 51.6% 12:3:161:3:1 CH 3 O 2:6:2 C2H6O2C2H6O2 30 C: 80% H: 20%12:3 4:1 1:3 CH 3 2:6 C2H6C2H6 128 C: 93.75% H: 6.25%60:4 15:1 5:4 C5H4C5H4 10:8 C 10 H 8 90 C: 26.7% H: 2.2% O: 71.1% 12:1:321:1:2 CHO 2 2:2:4 C2H2O4C2H2O4

28 (insert picture of your own choice)

29 Card sort with template (harder)

30 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 C 12 H 18 CH 2 O 180 C:H 78 Ca: 40% C: 12% O: 48% 100 SiH 4 32

31 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C:H:N 60 C: 75% H: 25%16 C:H:O 12:3:1662 C: 80% H: 20%30 C: 93.75% H: 6.25%128 C: 26.7% H: 2.2% O: 71.1% 90

32 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 3:6 CH 2 1:212:2 6:1 C: 85.7% H: 14.3%42 C 12 H 18 12:18 C2H3C2H3 2:324:3 8:1 C: 88.9% H: 11.1%162 C 6 H 12 O 6 6:12:6 CH 2 O 1:2:112:2:16 6:1:8 C:40% H 6.7% O: 53.3% 180 C6H6C6H6 6:6 CH 1:112:1 C: 92.3% H: 7.7%78 CaCO 3 1:1:3 CaCO 3 1:1:340:12:48 10:3:12 Ca: 40% C: 12% O: 48% 100 SiH 4 1:4 SiH 4 1:428:4 7:1 Si: 87.5% H: 12.5%32

33 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C2H8N2C2H8N2 2:6:2 CH 4 N 1:4:112:4:14 6:2:7 C:40% H: 13.3% N: 46.7% 60 CH 4 1:4 CH 4 1:412:4 3:1 C: 75% H: 25%16 C2H6O2C2H6O2 2:6:2 CH 3 O 1:3:112:3:16 C: 38.7% H: 9.7% O: 51.6% 62 C2H6C2H6 2:6 CH 3 1:312:3 4:1 C: 80% H: 20%30 C 10 H 8 10:8 C5H4C5H4 5:460:4 15:1 C: 93.75% H: 6.25%128 C2H2O4C2H2O4 2:2:4 CHO 2 1:1:212:1:32 C: 26.7% H: 2.2% O: 71.1% 90

34 Relative molecular mass (amu) % by massFraction of total mass for each element Ratio of masses Simplified Ratio Empirical formula RatioMolecular Formula 42 C: 85.7% H: 14.3%12:2 6:1 1:2 CH 2 3:6 C3H6C3H6 162 C: 88.9% H: 11.1%24:3 8:1 2:3 C2H3C2H3 12:18 C 12 H 18 180 C:40% H 6.7% O: 53.3% 12:2:16 6:1:8 1:2:1 CH 2 O 6:12:6 C 6 H 12 O 6 78 C: 92.3% H: 7.7%12:11:1 CH 6:6 C6H6C6H6 100 Ca: 40% C: 12% O: 48% 40:12:48 10:3:12 1:1:3 CaCO 3 1:1:3 CaCO 3 32 Si: 87.5% H: 12.5%28:4 7:1 1:4 SiH 4 1:4 SiH 4

35 (insert picture of your own choice)

36 Relative molecular mass (amu) % by massFraction of total mass for each element Ratio of masses Simplified Ratio Empirical formula RatioMolecular Formula 60 C:40% H: 13.3% N: 46.7% 12:4:14 6:2:7 1:4:1 CH 4 N 2:6:2 C2H8N2C2H8N2 16 C: 75% H: 25%12:4 3:1 1:4 CH 4 1:4 CH 4 62 C: 38.7% H: 9.7% O: 51.6% 12:3:161:3:1 CH 3 O 2:6:2 C2H6O2C2H6O2 30 C: 80% H: 20%12:3 4:1 1:3 CH 3 2:6 C2H6C2H6 128 C: 93.75% H: 6.25%60:4 15:1 5:4 C5H4C5H4 10:8 C 10 H 8 90 C: 26.7% H: 2.2% O: 71.1% 12:1:321:1:2 CHO 2 2:2:4 C2H2O4C2H2O4

37 (insert picture of your own choice)

38

39 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C3H6C3H6 3:6 CH 2 1:212:2 6:1 C: 85.7% H: 14.3%42 C 12 H 18 12:18 C2H3C2H3 2:324:3 8:1 C: 88.9% H: 11.1%162 C 6 H 12 O 6 6:12:6 CH 2 O 1:2:112:2:16 6:1:8 C:40% H 6.7% O: 53.3% 180 C6H6C6H6 6:6 CH 1:112:1 C: 92.3% H: 7.7%78 CaCO 3 1:1:3 CaCO 3 1:1:340:12:48 10:3:12 Ca: 40% C: 12% O: 48% 100 SiH 4 1:4 SiH 4 1:428:4 7:1 Si: 87.5% H: 12.5%32

40 Molecular Formula RatioEmpirical formula Simplified Ratio Ratio of masses Fraction of total mass for each element % by massRelative molecular mass (amu) C2H8N2C2H8N2 2:6:2 CH 4 N 1:4:112:4:14 6:2:7 C:40% H: 13.3% N: 46.7% 60 CH 4 1:4 CH 4 1:412:4 3:1 C: 75% H: 25%16 C2H6O2C2H6O2 2:6:2 CH 3 O 1:3:112:3:16 C: 38.7% H: 9.7% O: 51.6% 62 C2H6C2H6 2:6 CH 3 1:312:3 4:1 C: 80% H: 20%30 C 10 H 8 10:8 C5H4C5H4 5:460:4 15:1 C: 93.75% H: 6.25%128 C2H2O4C2H2O4 2:2:4 CHO 2 1:1:212:1:32 C: 26.7% H: 2.2% O: 71.1% 90

41 Alternative ratio activity

42 C2H2C2H2 C6H6C6H6 C2H4C2H4 C 6 H 12 C4H8C4H8 C2H4O2C2H4O2 CH 2 O C3H6O3C3H6O3 C 6 H 12 O 6 C2H6OC2H6O C 6 H 12 O 3 H2OH2O H2O2H2O2 C 5 H 10 C5H8OC5H8O Match the following molecules that contain the same ratio of elements. The simplest ratio of elements in a compound is called the empirical formula can you find the empirical formula for each compound?

43 Extension The mass of each of the compound is shown on the next slide. Can you work out the mass of the following atoms H (hydrogen) C (carbon O (oxygen)

44 C 2 H 2 26 C 6 H 6 78 C 2 H 4 28 C 6 H 12 84 C 4 H 8 56 C 2 H 4 O 2 60 CH 2 O 30 C 3 H 6 O 3 90 C 6 H 12 O 6 180 C 2 H 6 O 46 C 6 H 12 O 3 132 H 2 O 18 CH 4 16 C 5 H 10 70 C 5 H 8 O 84

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