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Measurement of Matter: The Mole

Measurement of Matter: The Mole. How do you measure matter? What are the three different ways we Can measure things? count mass volume. CONVERSIONS. A pair Equals A dozen equals 1 minute equals how many seconds? 1 hour equals how many minutes. 2 12 60 60.

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Measurement of Matter: The Mole

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  1. Measurement of Matter: The Mole • How do you measure matter? • What are the three different ways we Can measure things? count mass volume

  2. CONVERSIONS • A pair Equals • A dozen equals • 1 minute equals how many seconds? • 1 hour equals how many minutes • 2 • 12 • 60 • 60

  3. CHEMICAL QUANTITIES • http://www.youtube.com/watch?v=1R7NiIum2TI

  4. THE MOLE • How do we count matter? • Composed of atoms, molecules and ions • The mole is an equality that describes the number of particles in a substance • 6.02 x 10 23particles,atomsect.. = 1 mole ( avogadro’s number)

  5. Practice Problem • How many moles of magnesium is 1.25 x 1023 atoms of magnesium • 1. Start with what you know • 1.25 x 10 23 atoms of Mg 1 mole of Mg 6.02 X 10 23 atoms of mg = 0.208 mol Mg

  6. REVIEW 1. How many atoms are in 1.14 mol of SO3 2. How many moles are in 4.65 x10 24 molecules of NO2

  7. How many atoms are in 1.50 mols of Na • determine the number of moles in 4.96 x 10 24 molecules glucose

  8. Mass of a Mole in an element • The atomic mass of an element expressed in grams is the mass of a mole of the element = molar mass • Ex. Carbons molar mass = 12.0g Hydrogens molar mass = 1.0 g • The molar masses of any two elements contains the same number of atoms • 12.0 g of carbon = 1 mol = 6.02 x 10 23 particles • 1.0 g of hydrogen = 1 mol = 6.023 x 10 23 particles

  9. Mass of a mole of a compound • Must know the formula of the compound first • Ex. SO3 • 1 sulfur ( 1 x 32.1) 32.1 amu • 3 oxygen ( 3 x 16.0) = 48.0 amu • molar mass = 48.0 + 32.1 = 80.1 amu • 1 mol has a mass of 80.1 amu

  10. Review • What is the molar mass of PCl3 • How many atoms are in 1.50 mols of Na

  11. MASS/MOLE RELATIONSHIPS • Remember: to calculate molar mass you must know the number of grams of each element in one mole of the compound and add the masses of all the elements of the compound • You can use molar mass of an element or compound to convert between the mass of a substance and the moles of a substance

  12. calculations • Calculate the mass of 3.00 mol of NaCl • Molar Mass of NaCl • Na = 23.9 • Cl = 35.4 • Total = 53.9 g • 3.00 mol 54.9 g NaCl 1 mol NaCl

  13. Converting mass to moles • How many moles of Iron (III) oxide are contained in 92.2 g of Fe2O3 • 92.2 g of Fe2O3 X 1 mol of Fe2O3 160 g Fe2O3 = .58 mol Fe2O3

  14. GRAMS TO MOLECULES • How many grams are in 4.65 x10 24 molecules of NO2

  15. Review Quiz • How many grams are in 4.65 x10 24 molecules of NO2 • What is the molar mass of PCl3 • What is the mass of 2.25 mol of NaCl

  16. QUIZ • How many grams does • 4.3 x 1021 molecules of MgCl2 have

  17. PERCENT COMPOSITION • Percent Composition – the relative amounts of the elements in a compound • Consists of a percent value for each different element in a compound

  18. CALCULATIONS • The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100% • % mass of element = mass of element x 100 • mass of compound

  19. Practice • Propane (C3H8), the fuel commonly used in gas grills, is one of the compounds obtained from petroleum. Calculate the percent composition of propane • %C = 36.0g (3 X 12) x 100 = 81.8% 44.0g %H = 8.0g x 100 = 18% 44.0g

  20. REVIEW QUIZ • Propane (C3H8), the fuel commonly used in gas grills, is one of the compounds obtained from petroleum. Calculate the percent composition of propane • Calculate the number of moles in 0.50 g of sodium bromide (NaBr)

  21. Review Quiz; % composition • What is the percent composition of baking soda NaHCO3

  22. Empirical/Molecular Formulas • The lowest whole number ratio of the atoms of the elements in a compound • Molecular formula H2O2 • Empirical formula HO

  23. Determining empirical formulas • A compound is analyzed and found to contain 70.9% potassium and 29.1%sulfer. What is the empirical formula of the compound? • Percent you can assume 100 70.9 g x 1 mol K = 1.8molK 39 g K 29.1 g x 1 mol S = .91 mol S 32 g S HINT: % TO MASS MASS TO MOLE DIVIDE BY SMALLEST MULTIPLY TILL WHOLE

  24. Divide each molar quantity by the smaller number of moles 1.85/.91 = 2 K 1. = .91/.91 = 1 S K2S

  25. MOLECULAR FORMULAS • Molecular formulas can be determine by empirical formulas. • First calculate the empirical formula mass • Divide molecular mass by formula mass • Multiply each subscript in your formula by the factor

  26. Practice problem • A compound with an empirical formula of CH2O has a molecular mass of 90 amu. What is it’s molecular formula • Determine empirical formula mass • C = 12 x1 • H = 1 x 2 • O = 16 x 1 • 30

  27. Divide the molecular mass by the empirical formula mass to determine the multiple 90/30 = 3 Multiply the empirical formula by the multiple to find the molecular formula [CH2O] X 3 = C3H6O3

  28. REVIEW QUIZ • A compound has 67.6% Hg, 10.8% S, and 21.6% O. Determine the empirical formula • Find the molecular formula of ethylene glycol (antifreeze). The molar mass is 62g/mol and the empirical formula is CH3O

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