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February 28, 2014. Final Polyatomic Ion Quiz Due: HW 7B Percentage Composition Lab Report due Wednesday March 5 Today’s video: Oldest known piece of earth How old?! What do you think their “technique” is? Z irconium silicate -  ZrSiO 4. Percent Composition.

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february 28 2014
February 28, 2014
  • Final Polyatomic Ion Quiz
  • Due: HW 7B
  • Percentage Composition
  • Lab Report due Wednesday March 5
  • Today’s video: Oldest known piece of earth
    • How old?!
    • What do you think their “technique” is?
    • Zirconiumsilicate - ZrSiO4
percent composition
Percent Composition
  • Percent composition: Percentage by mass of each element in a compound.
  • What percent of gum is sweetener?
percent composition1
Percent Composition
  • Mass percentage of an element in a compound is the same regardless of the sample size. This is because the ratio of one element to another in a given compound is the same regardless of sample size.
  • H2O = 2 parts H : 1 part O
to calculate composition
To calculate % Composition
  • % element in compound =

n(Molar mass of element) x 100

Molar mass of compound

n = how many of that atom in the compound

what are hydrates
What are hydrates?
  • Ionic Compounds that include water in the crystal lattice
  • ZnSO47H2O
  • For every one formula unit of zinc sulfate, there are seven water molecules.
  • If heated, the water will leave
example carbon dioxide
Example: Carbon dioxide
  • Find the percentage composition of:
  • Carbon dioxide, CO2
    • Molar mass of CO2: 12.01 + 2(16.00) = 44.01 g/mol
    • % C: 12.01 g/mol x 100 = 27.29% C

44.01 g/mol

    • % O: 2(16.00 g/mol) x 100 = 72.71% O

44.01 g/mol

Check by adding the %s: 27.29 + 72.71 = 100.00%

example sodium nitrate
Example: Sodium nitrate
  • Find the percentage composition of:
  • Sodium nitrate
    • Molar mass of NaNO3: 22.99 + 14.01 + 3(16.00) = 85.00 g/mol
    • % Na: 22.99 g/mol x 100 = 27.05% Na

85.00 g/mol

    • % N: 14.01 g/molx 100 = 16.48% N
    • 85.00 g/mol
    • % O: 3(16.00 g/mol) x 100 = 56.47% O

85.00 g/mol

Check by adding the %s: 27.05 + 16.48 + 56.74 = 100.00%

practice pbcl 2
Practice: PbCl2
  • Find the percentage composition of:
  • Lead (II) Chloride
    • Molar mass of PbCl2: 207.2 + 2(35.453) = 278.106 g/mol
    • % Pb: 207.2 g/mol x 100 = 74.50% Pb

278.106 g/mol

    • % Cl: 2(35.453 g/mol) x 100 = 25.50% Cl

278.106 g/mol

Check by adding the %s: 74.50 + 25.50 = 100.00%

practice ba clo 3 2
Practice: Ba(ClO3)2
  • Find the percentage composition of:
  • Barium chlorate
    • Molar mass of Ba(ClO3)2 :
    • 137.33 + 2(35.453) + 6(15.999) = 304.23 g/mol
    • % Ba: 137.33 g/mol x 100 = 45.14% Ba

304.23 g/mol

    • % Cl: 2(35.453 g/mol) x 100 = 23.31% Cl

304.23 g/mol

    • % O: 6(15.999 g/mol) x 100 = 31.55% O

304.23 g/mol

Check by adding the %s: 47.14 + 23.31 + 31.55 = 100.00%

practice ch 4
Practice: CH4
  • Find the percentage composition of hydrogen in methane
    • Molar mass of CH4
    • 12.011 + 4(1.0079) = 16.0426 g/mol
    • % H: 4(1.0079) g/mol x 100 = 25.13 % H

16.0426 g/mol

practice znso 4 7h 2 o
Practice: ZnSO47H2O
  • Find the percentage composition of water in zinc sulfate heptahydrate.
    • Molar mass of ZnSO47H2O
    • 65.39 + 32.066 + 4(15.999) + 14(1.0079) + 7(15.999) = 287.561 g/mol
    • % H2O: 14(1.0079) + 7(15.999) g/molx 100

287.561 g/mol

= 43.85 % H2O

wait what are hydrates
Wait - What are hydrates?
  • Ionic compounds that include water in the crystal lattice.
  • ZnSO47H2O
  • For every one formula unit of zinc sulfate, there are seven water molecules.
  • The dot indicates ratio, not “multiply”
  • If heated, the water will leave the compound and the color will change.