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How you measure how much?

How you measure how much?. You can measure mass, or volume, or you can count pieces. We measure mass in grams. We measure volume in liters. We count pieces in MOLES. For modern systems; 12 C is taken as a standard. So; 12 C is assumed to be 12 a.m.u. 1 12 C = 12 a.m.u.

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How you measure how much?

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  1. How you measure how much? You can measure mass, or volume, or you can count pieces. We measure mass in grams. We measure volume in liters. We count pieces in MOLES.

  2. For modern systems; 12C is taken as a standard. So; 12C is assumed to be 12 a.m.u.1 12C = 12 a.m.u. 1 a.m.u.=1/12 of the mass of a single 12C atom =1/12 (12/6.02 X 1023) =1/6.02 X 1023 grams =mass of 1 1H atom Then by comparing the masses of each atom with the mass of 12C atomic masses of other atoms can be easily calculated “RELATIVE ATOMIC MASSES”. Relative atomic masses easily calculated by MASS SPECTROMETER. 116O = 16 a.m.u 1 40Ca = 40a.m.u. 1 1H = 1 a.m.u.

  3. Moles Defined as the number of carbon atoms in exactly 12 grams of carbon-12. 1 mole contains 6.02 x 1023 particles. Treat it like a very large dozen 6.02 x 1023 is called Avogadro’s number.

  4. Representative particles The smallest pieces of a substance. For a molecular compound it is a molecule. For an ionic compound it is a formula unit. For an element it is an atom.

  5. Units of measurement used with equations.We use a mole concept to bring together the concepts of counting numbers and atomic weights of elements.The mole is derived from the following information.Atomic weights are an average of the relative masses of all of the isotopes of the given element.The number of C-12 atoms in exactly 12.00 g of C-12 is 6.02 X 1023.This called Avogadro’s number.

  6. An amount of a substance that contains Avogadro’s number of atoms, ions, molecules, or any other chemical unit is called A MOLE. A mole of C-12 atoms is defined as having a mass of exactly 12.00 g, a mass that is equal to its atomic weight.

  7. Mole Calculations 1 mole (mol): Amount of matter that contains as many objects (atoms, molecules) as the number of atoms in isotopically pure 12C. 6.022 x 1023 Also known as Avogadro’s number. 1 mol 12C atoms = 6.02 x 102312C atoms 1 mol H2O molecules = 6.02 x 1023 molecules 1 mole NO3- ions = 6.02 x 1023 NO3- ions.

  8. The mole concept for (A) elements, (B) compounds, and (C) molecular substances. • A mole contains 6.02 X 1023 particles. Since every mole contains the same number of particles, the ratio of the mass of any two moles is the same as the ratio of the masses of individual particles making up the two moles.

  9. Molar Mass The atomic mass of any substance expressed in grams corresponds to 1 mol of the substance. Atomic mass of a substance expressed in grams is the molar mass. The molar mass of a diatomic substance is equal to twice its atomic mass.

  10. Molar Mass The generic term for the mass of one mole. The same as gram molecular mass, gram formula mass, and gram atomic mass.

  11. Gram Atomic Mass The mass of 1 mole of an element in grams. 12.01 grams of carbon has the same number of pieces as 1.008 grams of hydrogen and 55.85 grams of iron. We can right this as 12.01 g C = 1 mole We can count things by weighing them.

  12. Mole Calculations Calculate the number of sodium atoms in 0.120 mol Na? 0.120 mol Na x 6.02 x 1023 atoms Na = 7.22 x 1022 1 mol Na

  13. Mole Calculations Calculate the number of moles of potassium in 1.25 x 1021 atoms of K. 1.25 x 1021 atoms K x 1 mol K = 2.08 x 10-3 mol K 6.02 x 1023 atoms K

  14. Mole Calculations What is the mass in grams of 2.01 x 1022 atoms of sulfur? 2.01 x 1022 atoms S x 1 mol S x 32.07 g S 6.02 x 1023 atoms S 1 mol S = 1.07g S

  15. Mole Calculations How many O2 molecules are present in 0.470g of oxygen gas? 0.470 g O2 x 1mol O2 x 6.02 x 1023 molecules O2 32.00 g O2 1 mol O2 = 8.84 x 1021 molecules O2

  16. What about compounds? In 1 mole of H2O molecules there are two moles of H atoms and 1 mole of O atoms To find the mass of one mole of a compound determine the moles of the elements they have Find out how much they would weigh add them up.

  17. Molar Mass

  18. The Mole Calculate the number of Magnesium and Chlorine ions present in 0.450 mol of MgCl2. # Mg2+ ions: 0.450 mol MgCl2 x 6.02 x 1023 formula units x 1 Mg2+ 1 mole 1 formula unit # Mg2+ ions = 2.71 x 1023 # Cl- ions: 0.450 mol MgCl2 x 6.02 x 1023 formula units x 2 Cl- 1 mole 1 formula unit # Cl- ions = 5.42 x 1023

  19. The mole concept applied to compounds • The formula weight of a species is the sum of • atomic masses (amu) of the atoms in a species. • Molecular weight of NH3 = • For an ionic cmpd formula weight MgF2 =

  20. Mass of one mole of MgF2 is Mass of one formula unit of MgF2 is Mass of 6.022 x 1023 formula units of MgF2 is

  21. Gram Formula Mass The mass of one mole of an ionic compound. Calculated the same way. What is the GFM of Fe2O3? 2 moles of Fe x 55.85 g = 111.70 g 3 moles of O x 16.00 g = 48.00 g The GFM = 111.70 g + 48.00 g = 159.70g

  22. Molar Mass

  23. What about compounds? What is the mass of one mole of CH4? 1 mole of C = 12.01 g 4 mole of H x 1.01 g = 4.04g 1 mole CH4 = 12.01 + 4.04 = 16.05g The Gram Molecular mass of CH4 is 16.05g The mass of one mole of a molecular compound.

  24. The gram atomic weight of an element is the mass in grams of one mole of an element that is numerically equal to its atomic weight. The gram formula weight of a compound is the mass in grams of one mole of the compound that is numerically equal to its formula weight. The gram formula weight of a compound is the sum total of all the individual atomic weight in the formula.The gram molecular weight is the gram formula weight of a molecular compound.

  25. Molar Mass Calculate the molar mass of Ag and of magnesium nitrate, Mg(NO3)2. Ag is an element so its molar mass equals its atomic mass = 107.87g/mol. Mg(NO3)2 = 24.31 + 2(14.01 + 3 x 16.00) = 148.33 g/mol

  26. For example How many moles is 5.69 g of NaOH? • need to change grams to moles • for NaOH • 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g • 1 mole NaOH = 40.00 g

  27. Mole Calculations Calculate the mass in grams of a single molecule of carbon dioxide, CO2. 44.01 g CO2 x 1mol CO2 = 7.31 x 10-23 g/molecule 1 mol CO2 6.02 x 1023 molecules

  28. Molar Mass The number of grams of 1 mole of atoms,ions,or molecules. We can make conversion factors from these. To change grams of a compound to moles of a compound.

  29. Examples How many moles is 4.56 g of CO2 ? How many grams is 9.87 moles of H2O? How many molecules in 6.8 g of CH4? 49 molecules of C6H12O6 weighs how much?

  30. Calc the molar mass of Ca(NO3)2. Calc the molar mass of a compound if 0.372 mol of it has a mass of 152g.

  31. How many grams of each are required to have 0.100 mol of A. NaOH B. H2SO4 C. C2H5OH D. Ca3(PO4)2

  32. How many moles are in 50.0 g of A. CS2 B. Al2(CO3)3 C. Sr(OH)2 D. LiNO3

  33. Calc the no. of C, H, and O atoms in 1.50 g of glucose (C6H12O6). What is the average mass of one C3H8 molecule? What is the mass of 5.00 x 1024 molecules of NH3?

  34. Types of questions How many molecules of CO2 are the in 4.56 moles of CO2 ? How many moles of water is 5.87 x 1022 molecules? How many atoms of carbon are there in 1.23 moles of C6H12O6 ? How many moles is 7.78 x 1024 formula units of MgCl2?

  35. Gases Many of the chemicals we deal with are gases. They are difficult to weigh. Need to know how many moles of gas we have. Two things effect the volume of a gas Temperature and pressure Compare at the same temp. and pressure.

  36. Standard Temperature and Pressure 0ºC and 1 atm pressure abbreviated STP At STP 1 mole of gas occupies 22.4 L Called the molar volume Avogadro’s Hypothesis - at the same temperature and pressure equal volumes of gas have the same number of particles.

  37. Molar Volume Avogadro's Theory: Two gases containing equal numbers of molecules occupy equal volumes under similar conditions. Standard Temperature and Pressure: 0OC and 1 atm. Molar Volume at STP = 22.4 L

  38. Examples What is the volume of 4.59 mole of CO2 gas at STP? How many moles is 5.67 L of O2 at STP? What is the volume of 8.8g of CH4 gas at STP?

  39. Molar Volume Density of gas = molar mass in grams molar volume in liters Calculate the density of ammonia gas, NH3, at STP. Density of NH3 = molar mass NH3 = 17.04g molar volume NH3 22.4 L = 0.761 g/L

  40. Density of a gas • D = m /V • for a gas the units will be g / L • We can determine the density of any gas at STP if we know its formula. • To find the density we need the mass and the volume. • If you assume you have 1 mole then the mass is the molar mass (PT) • At STP the volume is 22.4 L.

  41. Examples Find the density of CO2at STP. Find the density of CH4 at STP.

  42. Mass Volume 22.4 L PT Moles 6.02 x 1023 Representative Particles Ions Atoms

  43. Mole Calculations What is the mass of 3.36 L of ozone gas, O3, at STP? 3.36 L O3 x 1 mol O3 x 48.00g O3 = 7.20 g O3 22.4 L O3 1 mol O3

  44. Mole Calculations How many molecules of hydrogen gas, H2, occupy 0.500 L at STP? 0.500 L H2 x 1 mol x 6.02 x 1023 molecules H2 22.4 L 1 mol = 1.34 x 1022 molecules H2

  45. Mole Calculations

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