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CHEMICAL QUANTITIES

CHEMICAL QUANTITIES. THE MOLE CONCEPT AND ITS APPLICATIONS. Chemical Quantities. Objectives Students will be able to Understand and know the definitions of the mole and Avogadro’s Number relationship between moles and mass relationship between moles and particles

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CHEMICAL QUANTITIES

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  1. CHEMICAL QUANTITIES THE MOLE CONCEPT AND ITS APPLICATIONS

  2. Chemical Quantities Objectives • Students will be able to • Understand and know • the definitions of the mole and Avogadro’s Number • relationship between moles and mass • relationship between moles and particles • Calculate the formula mass of a compound given the periodic table • Calculate the mass percent composition of a compound given the formula, formula mass, and periodic table.

  3. Drill & Objectives • How many eggs are there in a dozen? • If I bought 3 dozen eggs, how many eggs do I have? • What are some ways that you can measure things? (such as the amount of a substance) Objectives • Students will be able to • Understand and know • the definitions of the mole and Avogadro’s Number • relationship between moles and mass • relationship between moles and particles • Calculate the formula mass of a compound given the periodic table • Calculate the mass percent composition of a compound given the formula, formula mass, and periodic table.

  4. Chemical Quantities • How many eggs are there in a dozen? 12!

  5. Chemical Quantities • How many roses are there in a dozen roses? 12!

  6. Chemical Quantities • Does it matter what the _____________ is?

  7. Chemical Quantities • Does it matter what the _____________ is? • NO! A Dozen is a dozen! No matter if it’s flowers, eggs, bagels, ect. • It represents a number of _______

  8. Chemical Quantities • In Chemistry the same concept is valid, • Let’s talk about “The Mole” and how it relates to Chemistry…

  9. The Mole?

  10. The Mole?

  11. The Mole? • “The Mole” or “A Mole” is an amount of a substance • There are 6.02 x1023 atoms (representative particles of a substance) in 1 Mole (of that substance). • This number (6.02 x1023) is called Avogadro’s number • Named after Amedeo Avogadro diQuarenga (1776 – 1856), an Italian scientist.

  12. The Mole! • Let’s put this into perspective • How much is 1 mol of a substance? 6.023 x 1023!!

  13. The Mole! • IF you had 6.02 X 1023  Watermelon Seeds…

  14. The Mole! • IF you had 6.02 X 1023  Watermelon Seeds… it would be found inside a watermelon slightly larger than the moon!

  15. The Mole! • If you had 6.02 X 1023 Grains of Sand…

  16. The Mole! • IF you had 6.02 X 1023 Grains of Sand… it would be more than ALL the sand on Miami Beach.

  17. The Mole? • A mole is the amount of substance or representative particles of any substance. • Therefore, as we have just seen • 1 mol of N2 there are 6.02x1023MOLECULES of N2 • 1 mol of C12H22O11 has how many molecules? 6.02x1023 can be used for “atoms” if they are the same element OR It can be used for “molecules” for many elements that are together, via compounds.

  18. Chemical Quantities • How many moles of Magnesium is 3.01x1022 atoms of magnesium? Step 1 - What do we know? We know that there are 3.01x1022 atoms of Mg Step 2 - What do we want know? We want to know the number of moles of Mg Step 3 – What do we know that can be used for these conversions? We know that there are 6.02x1023 atoms in 1 mol Step 4 – Solve the problem

  19. Chemical Quantities • How many moles of Magnesium is 3.01x1022 atoms of magnesium? 1 mol Mg 3.01x1022 atoms Mg X 6.02x1023 atoms of Mg = 5.00x10-2 mol Mg

  20. Chemical Quantities • Individual Problems • How many moles are 1.20x1025 atoms of phosphorus? • How many atoms are in 0.750 mol of Zinc? • How many molecules are there in 4 mol of glucose, C6H12O6? • How many molecules are there in 0.44 mol N2O5

  21. Chemical Quantities • Now there is a difference between asking how many atoms are there in the entire compound and how many atoms of one of the compound there are. • We said that there are the same number or atoms in a compound or a diatomic molecule. However, there is a difference between these questions… • How many atoms are there in aluminum fluoride? VS. • How many fluoride ions are there in aluminum fluoride?

  22. Chemical Quantities • So let’s answer the question. • How many fluoride ions are there in 1.46 mol of aluminum fluoride? • If we follow the four steps that we went through prior

  23. Chemical Quantities How many fluoride ions are there in 1.46 mol of aluminum fluoride? Step 1 - What do we know? We know that there are 1.46 mol of aluminum fluoride Step 2 - What do we want know? We want to know the number of F- Step 3 – What do we know that can be used for these conversions? NO! We know that there are 6.02x1023 atoms in 1 mol BUT is that enough information??

  24. Chemical Quantities How many fluoride ions are there in 1.46 mol of aluminum fluoride? • We want to know the number of F- • But how can we find out the number of fluoride ions we have from what is given? We can get the information we need by writing out the chemical formula of the compound. AlF3

  25. Chemical Quantities How many fluoride ions are there in 1.46 mol of aluminum fluoride? 6.02x1023 Formula units of AlF3 1.46 mol AlF3 X X 1 mol AlF3 3 F- ions = 26.3676 x 1023 F- ions 1 formula unit AlF3

  26. Individual Work • How many ammonium ions are in 0.036 mol ammonium phosphate, (NH4)3PO4?

  27. DRILL • What is Avogadro's number? • How many particles are there in 1 mol of a substance? • How many atoms are there in 1.45 mol of Na?

  28. Chemical Quantities The Gram Formula Mass

  29. Chemical Quantities • Chemists have defined the gram atomic mass as the number of grams of an element that is numerically equal to the atomic mass in amu • The Gram atomic mass is the mass of one mole of atoms of a monatomic element • This can also be described as MOLAR MASS – in place of gram formula mass to refer to the mass of a mole of any element or compound. • I will be using the term Molar Mass more frequently

  30. Chemical Quantities Atomic Mass Number

  31. Chemical Quantities This number tells you how many grams of this element there are in 1 mol of the element Therefore, there are47.88 grams/mol of Ti Or there are47.88 grams of Ti IN 1 mol of Ti

  32. Chemical Quantities The molar mass in grams/mol

  33. Chemical Quantities • You can calculate the total molecular weight of a molecule by adding up the molar masses of each element. • The molar mass of the molecule SO4 is equal to S = 32.065 g/mol x 1 S = 32.065 g/mol O = 15.9994 g/mol x 4 O = 63.9976 g/mol SO4 = 96.0626 g/mol • I will specify the amount of significant figures needed in your answer

  34. Individual Work • What is the molar mass of the following compounds? REMEMBER YOUR UNITS! • PCl3 • Sodium Carbonate • C8H18 • Aluminum Sulfate • (NH4)2CO3

  35. Chemical Quantities • Why is this important? • This is important because it will allow us to covert from moles to grams and grams to moles, allowing for quantitative experimentation. • Let’s do a calculation… • How many grams are in 7.20 mol of dinitrogen trioxide?

  36. Chemical Quantities How many grams are in 7.20 mol of dinitrogen trioxide? • Step 1 – add up the total molar mass of the compound • If it is in word form, write the chemical formula • Step 2 – Set up the proper conversion factors • Step 3 – Solve

  37. Chemical Quantities How many grams are in 7.20 mol of dinitrogen trioxide? • Step 1 – add up the total molar mass of the compound • If it is in word form, write the chemical formula N2O3 N = 14.0 g/mol x 2 N = 28.0 g/mol O = 16.0 g/mol x 3 O = 48.0 g/mol N2O3 = 76.0 g/mol

  38. Chemical Quantities How many grams are in 7.20 mol of dinitrogen trioxide? • Step 2 – Set up the proper conversion factors • Step 3 – Solve

  39. Individual Work • Find the mass of the following • 3.32 mol K • 5.08 mol Ca(NO3)2 • 4.52x10-3 mol K2CO3 • Find the number moles of the following • 0.000264g Li2HPO4 • 847g (NH4)2CO3 • 195g calcium nitrate

  40. Exit Ticket • Does 54.938 g of Mn have the same number of moles as that of 112.411 g of Cd? Explain why or why not.

  41. DRILL • What is Avogadro’s number? • How many moles are there in 245 kg of CH2COOH? • Does 54.938 g of Mn have the same number of moles as that of 112.411 g of Cd? Explain why or why not.

  42. Group Work • Find the mass (g) of the following: • 10.0 mol Cr • 2.20x10-3 mol Sn • 0.720 mol Be • 2.40 mol N2 • 4.52x10-3 mol C20H42 • 0.0112 mol Potassium Carbonate • Find the number of moles of the following: • 72.0 gAr • 3.70x10-1 g B • 333 g Tin (II) Fluoride • 7.21x10-2g He • 27.4 g TiO2

  43. Chemical Quantities The Volume of a Mole of Gas

  44. Chemical Quantities How would we measure the amount of moles in a gas?

  45. Chemical Quantities • The volume of a gas is usually measured at STP (Standard Temperature and Pressure) • STP conditions • Temperature • 0°C • Pressure • 1 atmosphere (atm)

  46. Chemical Quantities At STP conditions 1 mol of ANY gas occupies a volume of 22.4 Liters (L) 22.4 Liters of a gas / 1 mol of the gas 22.4 L of a gas contains 6.02 x 1023 representative particles of that gas This is known as the molar volume of a gas

  47. Chemical Quantities What were the units of the molar volume of a gas? Liters What kind of unit is liters? VOLUME Therefore, 1 mol of any gas occupies the same volumenotmass

  48. Chemical Quantities He 22.4 L N2 6.02 x 1023 molecules of N2 28g of N2 Ne 22.4 L CO2 6.02 x 1023 molecules of CO2 44g of CO2 CO2 22.4 L He 6.02 x 1023 molecules of He 4g

  49. Individual Work What is the volume at STP of these gases? 5.40 mol O2 3.20 x 10-2 mol CO2 Assuming STP conditions, how many moles are there in these volumes 74.6 L SO2 5.78x10-2 N2

  50. Chemical Quantities Because the molar volume of a gas is a VOLUME, we can relate density (mass over volume) of a gas to determine the mass of the gas. If we have a gas that has a density of 1.964 g/L we can multiply the density with the molar volume of a gas (22.4 L) to calculate the mass of the gas. 1.964 x 22.4 L = 44.0g

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