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Chapter 10

Chapter 10. Chemical Quantities. Measuring Matter. measure the amt of something by by count, by mass, and by volume. Measuring Matter (1). Atoms, molecules and formula units are extremely small. so many of them in even the smallest sample that it’s impossible to actually count.

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Chapter 10

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  1. Chapter 10 Chemical Quantities

  2. Measuring Matter measure the amt of something by by count, by mass, and by volume.

  3. Measuring Matter (1) • Atoms, molecules and formula units are extremely small. • so many of them in even the smallest sample that it’s impossible to actually count. • Counting unit: mole.

  4. Measuring Matter (2) • mole (mol) • SI base unit used to measure the amt (# of representative particles) of a sub. • 1 mole of C = • # C atoms in exactly 12 g pure C-12 = • 6.02 x 1023 atoms of C

  5. Representative particles

  6. Measuring Matter (3) 1 mole of anything contains 6.02 x 1023 rep particles. Avogadro’s # atoms, molecules, formula units, e-, ions.

  7. What is a Mole? (1)

  8. Measuring Matter (4) 6.02 x 1023 -----Avogadro’s number (A) 602,000,000,000,000,000,000,000

  9. Question 1 Calculate the # of molecules in 15.7 mol CO2.

  10. Answer 9.45 x 1024 molecular CO2

  11. Convert moles to # of atoms Propane is a gas used for cooking and heating. How many atoms are in 2.12 mole of propane (C3H8).

  12. Measuring Matter (6) The rep particle in H2O is watermolecule.

  13. Measuring Matter The rep particle in Cu is Cuatom.

  14. Measuring Matter The rep particle in NaCl is NaCl formula unit.

  15. Converting Moles to Particles Find how many particles of sucrose are in 3.50 moles of sucrose. • 1 mole contains 6.02 x 1023 rep particles. • write a conversion factor that relates rep particles to moles of a sub.

  16. Converting Moles to Particles • There are 2.11 x 1024 molecules of sucrose in 3.50 moles.

  17. Question 2 Calculate the # of moles in 9.22 x 1023 atom Fe.

  18. Answer 1.53 mol Fe

  19. Converting Particles to Moles Zn is used as a corrosion-resistant coating on iron and steel. It is also an essential trace element in your diet. Calculate the # mol that contain 4.50 x 1024 atoms Zn.

  20. Converting Particles to Moles • Multiply the # Zn atoms by the conversion factor that is the inverse of Avogadro’s #.

  21. The Mass of a Mole • molar mass • mass in g of 1 mole of any pure sub (an element or a cpd) • molar mass of any element= its atomic mass • has the units g/mol. • molar mass of a cpd= sum of the # of g of each element in one mole of the cpd • has the units g/mol

  22. Converting Mass to Moles • A roll of Cu wire has a mass of 848 g. • How many moles Cu are in the roll? • Use the atomic mass Cu given on the PT to apply a conversion factor to the mass given.

  23. Converting Moles to Mass Calculate the mass of 0.625 moles of Ca. • Use the molar mass Ca to apply a conversion factor to the # moles given. • According to the PT, the atomic mass Ca is 40.078 amu. • So the molar mass Ca is 40.078 g.

  24. Converting Moles to Mass

  25. Question 3 Calculate the mass of 6.89 mol Sb.

  26. Answer 839g Sb

  27. Question 4 A chemist needs 0.0700 mol Se for a rxn. What mass Se should the chemist use?

  28. Answer 5.53g Se

  29. Converting Mass to # of Particles Calculate the # atoms in 4.77 g Pb. • To find the # of atoms in the sample, you must first determine how many moles are in 4.77 g Pb.

  30. Converting Mass to # of Particles According to data from the PT, the molar mass of Pb is 207.2 g/mol. Apply a conversion factor to convert mass to moles.

  31. Converting Mass to # of Particles Now use a 2nd conversion factor to convert moles to # particles.

  32. Converting Mass to # of Particles • Convert from # particles to mass # moles = # particles divided by Avogadro’s # Mass = # moles multiplied by molar mass

  33. Moles of Cpds • 1 mole is Avogadro’s # (6.02 x 1023) of particles of a sub. • If the sub is a molecular cpd (e.g. ammonia (NH3), a mole is 6.02 x 1023molecules of NH3. • If the sub is an ionic cpd (e.g. baking soda-- NaHCO3), a mole is 6.02 x 1023formula units of NaHCO3

  34. Moles of Cpds 1 mole of a cpd contains as many moles of each element as are indicated by the subscripts in the formula for the cpd. • e.g. 1 mole NH3 consists of 1 mole N atoms and 3 moles H atoms.

  35. Molar Mass of a Cpd • The molar mass of a cpd is the mass of 1 mole of the rep particles of the cpd. • Because each rep particle is composed of 2 or more atoms, the molar mass of the cpd is found by adding the molar masses of all of the atoms in the rep particle.

  36. Molar Mass of a Cpd molar mass NH3 = mass 1 mole N atoms + the mass 3 moles H atoms.

  37. Molar Mass of a Cpd Molar mass NH3 = molar mass N + 3 (molar mass H) Molar mass NH3 = 14 g + 3(1g) = 17 g/mol You can use the molar mass of a cpd to convert between mass and moles

  38. Converting Mass of a Cpd to Moles molar mass H2O = 2(molar mass H) + molar mass O • The molar mass H2O as a conversion factor to determine moles H2O. • Notice that 1.000 kg is converted to • 1.000 x 103 g for the calculn.

  39. Converting Mass of a Cpd to Moles

  40. Molar Volume (1) • Molar volume • Volume of a mole of gas STP • std temp (0°C or 273 K) and pressure (1 atm pressure or 101.3kPa)

  41. Molar Volume (2) At STP, 1 mol of any gas occupies a vol of 22.4 L At STP, volume of any gas is 22.4L At STP, density of a gas = molar mass divided by molar volume = molar mass (g) divided by 22.4 L

  42. Molar Volume (2) What is the vol of 3.20 x 10-3 mol CO2 at STP?

  43. Molar Volume (3) What is the vol of 3.70 mol N2 at STP?

  44. Molar Volume (4) At STP, what volume do 1.25 mol He occupy?

  45. Molar Volume (5) At STP, what vol. do 0.335 mol C2H6 occupy?

  46. Question 5 Calculate the # of moles in 17.2 g of benzene (C6H6).

  47. Answer 0.220 mol C6H6

  48. How many moles of CH4 are contained in 96.0 g of CH4? CST example 1 A 3.00 moles B 6.00 moles C 12.0 moles D 16.0 moles

  49. How many moles of C-12 are contained in exactly 6 g of C-12? CST example 2 A 0.5 moles B 2.0 moles C 3.01 x 1023 moles D 6.02 x 1023 moles

  50. How many atoms are contained in 97.6 g of platinum (Pt)? CST example 3 A 5.16 x 1030 B 3.01 x 1023 C 1.20 x 1024 D 1.10 x 1028

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