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Aim: what is Gram Formula mass? Do Now : What is a mole? Homework : None

Aim: what is Gram Formula mass? Do Now : What is a mole? Homework : None. Gram Formula Mass. Mg + 2HCl  H 2 + MgCl 2. We know magnesium and hydrochloric acid react to produce hydrogen gas ( we saw this in lab when you lit the sticks and put them in hydrogen gas you heard a pop)

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Aim: what is Gram Formula mass? Do Now : What is a mole? Homework : None

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  1. Aim: what is Gram Formula mass? Do Now: What is a mole? Homework: None

  2. Gram Formula Mass

  3. Mg + 2HCl  H2 + MgCl2 • We know magnesium and hydrochloric acid react to produce hydrogen gas ( we saw this in lab when you lit the sticks and put them in hydrogen gas you heard a pop) • As chemists we need to know how much to mix and how much will be produced.

  4. Counting Things • A Pair of shoes = 2 • Eggs come in dozens = 12 • Molecules come in moles = 6.02 X 1023

  5. Molar Mass • Molar mass – the molar mass of a substance is equal to the mass in grams of one molecule, or 6.02 x1023 Particles of the substance

  6. Formula Mass • Formula mass- the formula mass of any molecule, formula unit, or ion is the sum of the average atomic mass’s of all atoms represented in its formula.

  7. Formula mass and molar mass • Note these are two different terms but both are calculated the same way.

  8. How do you find the formula mass? • Write the correct formula for the compound. • Look up the atomic mass of each element in the compound and round it to the tenths place. • Multiple the atomic mass by the subscript of the element. • Then add all of the numbers together and you will have the formula mass. • The unit will be g/mol

  9. Find the formula mass for calcium phosphate? • The Formula: Ca3(PO4)2 • Ca = 40.1 x 3 = 120.3 • P = 31.0 x 2 = 62 • O = 16.0 x 8 = 128 • Total mass = 310.3 g/mol

  10. Find the Formula mass for Glucose? • C6H12O6 • C = 12 x 6 = 72 • H = 1 x 12 = 12 • O = 16 x 6 = 96 • Total Mass = 180

  11. Aim: What is a mole? Do Now: Calculate the molar mass of Calcium Chloride? (round to the tenths place) Homework: Castle Learning Assignment #1 Quarter 3, Quiz Tuesday

  12. StoichiometryUnit V

  13. I. The Mole a) Definition: An arbitrary unit used in chemistry to unite three measured properties of matter: • Mass • Volume • # of particles • Similar to a dozen, except instead of 12, it’s • 6.02 X 1023 (in scientific notation) This number is named in honor of Amedeo Avogadro (1776 – 1856)

  14. II. Molar Mass a) Definition: the mass of 1 mole (in grams) • Equal to the numerical value of the average atomic mass (get from periodic table), or add the atoms together for a molecule 1 mole of C atoms = 12.0 g 1 mole of Mg atoms = 24.3 g 1 mole of O2 molecules = 32.0 g

  15. b) Molar Mass of Compounds • The molar mass (MM) of a compound is determined the same way, except now you add up all the atomic masses for the molecule (or compound) • Ex. Molar mass of CaCl2 Element # of atoms Atomic Mass • Calcium = 1 X 40.08g = 40.08g • Chlorine = 2 X 35.45g = 70.90g • Molar Mass of calcium chloride = 110.98 g/mol

  16. Practice • Calculate the Molar Mass of Clacium Flouride • Formula = • Gram Atomic Mass • Ca: 1 X 40.1 = • F: 2 X 19.0 = • Molar Mass = CaF2 40.1g 38.0 g 78.1g

  17. 1. Converting Moles to Mass • Find the molar mass of the substance. • Multiply the molar mass by the number of moles of the substance. Ex: Find the mass of 4.5 moles of Calcium Sulfate Chemical Name: Calcium Sulfate Chemical Formula: CaSO4 Ca = 1 X 40.08 = 40.08 S = 1 X 32.06 = 32.06 O = 4 X 15.9994 = 63.9976 Molar Mass = 136.1 g/mol 136.1 g/mol X 4.5 mol = 612.6 g

  18. 2. Converting Mass to Moles • Find the molar mass of the substance. • Divide the given mass by the molar mass to determine the number of moles. Ex: Find the number of moles in 450 g of glucose (C6H12O6 ). C = 6 X 12.0111 = 72.0666 H = 12 X 1.00794 = 12.09528 O = 6 X 15.9994 = 95.9964 Molar Mass = 180.16 g/mol Given Mass/Molecular Mass = 450 g ÷ 180.16 g/mol = 2.5 moles

  19. Aim: How can we figure out molar volume? Do Now: How many grams do you have of water if you have a container with 1.6 moles of water? Homework: Complete the worksheet

  20. III. Molar Volume • a) Definition: the volume of 1 mole of a substance (in liters) • One mole of any gas at STP occupies a volume of 22.4 liters. • 1 mole of CO2 (g) molecules = 22.4 liters • 1 mole of N2 (g) molecules = 22.4 liters • 1 mole of O2 (g) molecules = 22.4 liters

  21. 1. Converting moles to volume • Multiply the number of moles of the chemical (given) by 22.4. Practice: 2.0 moles of CO2 (g) = ____________liters 0.5 moles of O2 (g) = ____________liters 4.0 moles of CH4 (g) = ________________liters

  22. 2. Converting volume to moles • Divide the volume of the chemical (given) by 22.4. Practice: _____moles of N2 (g) = 33.6 liters _____moles of H2 (g) = 5.6 liters _____moles of CCl4 (g) = 56.0 liters

  23. IV. Molesand Particle Number a)Avagadro’s Hypothesis states that the number of particles found in one mole of any chemical substance is 6.02 X 1023. Practice 1 mole of CO2 (g) molecules = 6.02 X 1023 1 mole of Ca (s) atoms = 6.02 X 1023 1 mole of O2 (g) molecules = 6.02 X 1023

  24. 1. Converting moles to particles • Multiply the number of the moles (given) by 6.02 X 1023. Practice: 1.5 moles of N2 (g) = _________molecules 0.5 moles of H2 (g) = _________molecules 1.75 moles of Ag(s) = _________atoms

  25. 1. Converting particles to moles • Divide the number of the particles (given) by 6.02 X 1023. Practice: _____moles of N2 (g) = 1.5 X 1023 molecules _____moles of Cu (s) = 12.04 X 1023 atoms _____moles of CH3OH(l) = 1.806 X 1024 molecules

  26. Gram Atomic (Formula) Mass Multiply by atomic/molar mass from periodic table Divide by atomic/molar mass from periodic table Moles Multiply by 6.02 X 1023 Multiply By 22.4 Divide By 22.4 Divide by 6.02 X 1023 Volume Atoms or Molecules

  27. V. From Particles (atoms/molecules) to mass(and mass to particles) How many atoms of Cu are present in 35.4 g of Cu?

  28. Learning Check! What is the mass (in grams) of 1.20 X 1024 molecules of glucose (C6H12O6)?

  29. Chemistry Recipes • Looking at a reaction tells us how much of something you need to react with something else to get a product. • Be sure you have a balanced reaction before you start! • Example: 2 Na + Cl2  2 NaCl • This reaction tells us that by mixing 2 moles of sodium atoms with 1 mole of chlorine molecules we will get 2 moles of sodium chloride • What if we wanted 4 moles of NaCl? 10 moles? 50 moles?

  30. Practice • Write the balanced reaction for hydrogen gas reacting with oxygen gas. 2 H2 + O2 2 H2O • How many moles of reactants are needed? • What if we wanted 4 moles of water? • What if we had 3 moles of oxygen, how much hydrogen would we need to react and how much water would we get? • What if we had 50 moles of hydrogen, how much oxygen would we need and how much water produced? 2 mol H21 mol O2 4 mol H22 mol O2 6 mol H2, 6 mol H2O 25 mol O2, 50 mol H2O

  31. Mole Ratios • These mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemical • Example: How many moles of chlorine is needed to react with 5 moles of sodium (without any sodium left over)? 2 Na + Cl2 2 NaCl

  32. Mole-Mole Conversions • How many moles of sodium chloride will be produced if you react 2.6 moles of chlorine gas with an excess (more than you need) of sodium metal? 2 Na + Cl2 2 NaCl

  33. Mole-Mass Conversions • Most of the time in chemistry, the amounts are given in grams instead of moles • We still go through moles and use the mole ratio, but now we also use molar mass to get to grams • Example: How many grams of chlorine are required to react completely with 5.00 moles of sodium to produce sodium chloride? 2 Na + Cl2 2 NaCl

  34. Practice • Calculate the mass in grams of Iodine required to react completely with 0.50 moles of aluminum. 2 Al + 3 I2  2 AlI3

  35. Mass-Mole • We can also start with mass and convert to moles of product or another reactant • We use molar mass and the mole ratio to get to moles of the compound of interest • Calculate the number of moles of ethane (C2H6) needed to produce 10.0 g of water • 2 C2H6 + 7 O2 4 CO2 + 6 H20

  36. Practice Calculate how many moles of oxygen are required to make 10.0 g of aluminum oxide 4 Al + 3 O2 2 Al2O3

  37. Mass-Mass Conversions • Most often we are given a starting mass and want to find out the mass of a product we will get (called theoretical yield) or how much of another reactant we need to completely react with it (no leftover ingredients!) • Now we must go from grams to moles, mole ratio, and back to grams of compound we are interested in

  38. Mass-Mass Conversion • Ex. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen. • N2 + 3 H2  2 NH3 2.00g N2 1 mol N2 2 mol NH3 17.06g NH3 28.02g N2 1 mol N2 1 mol NH3 = 2.4 g NH3

  39. Practice • How many grams of calcium nitride are produced when 2.00 g of calcium reacts with an excess of nitrogen?

  40. Limiting Reactant: Cookies 1 cup butter 1/2 cup white sugar 1 cup packed brown sugar 1 teaspoon vanilla extract 2 eggs 2 1/2 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 2 cups semisweet chocolate chips Makes 3 dozen If we had the specified amount of ingredients listed, could we make 4 dozen cookies? What if we had 6 eggs and twice as much of everything else, could we make 9 dozen cookies? What if we only had one egg, could we make 3 dozen cookies?

  41. Limiting Reactant • Most of the time in chemistry we have more of one reactant than we need to completely use up other reactant. • That reactant is said to be in excess (there is too much). • The other reactant limits how much product we get. Once it runs out, the reaction s. This is called the limiting reactant.

  42. Limiting Reactant • To find the correct answer, we have to try all of the reactants. We have to calculate how much of a product we can get from each of the reactants to determine which reactant is the limiting one. • The lower amount of a product is the correct answer. • The reactant that makes the least amount of product is the limiting reactant. Once you determine the limiting reactant, you should ALWAYS start with it! • Be sure to pick a product! You can’t compare to see which is greater and which is lower unless the product is the same!

  43. LimitingReactant Limiting Reactant: Example • 10.0g of aluminum reacts with 35.0 grams of chlorine gas to produce aluminum chloride. Which reactant is limiting, which is in excess, and how much product is produced? 2 Al + 3 Cl2 2 AlCl3 • Start with Al: • Now Cl2: 10.0 g Al 1 mol Al 2 mol AlCl3 133.5 g AlCl3 27.0 g Al 2 mol Al 1 mol AlCl3 = 49.4g AlCl3 35.0g Cl2 1 mol Cl2 2 mol AlCl3 133.5 g AlCl3 71.0 g Cl2 3 mol Cl2 1 mol AlCl3 = 43.9g AlCl3

  44. LR Example Continued • We get 49.4g of aluminum chloride from the given amount of aluminum, but only 43.9g of aluminum chloride from the given amount of chlorine. Therefore, chlorine is the limiting reactant. Once the 35.0g of chlorine is used up, the reaction comes to a complete .

  45. Limiting Reactant Practice • 15.0 g of potassium reacts with 15.0 g of iodine. Calculate which reactant is limiting and how much product is made.

  46. Finding the Amount of Excess • By calculating the amount of the excess reactant needed to completely react with the limiting reactant, we can subtract that amount from the given amount to find the amount of excess. • Can we find the amount of excess potassium in the previous problem?

  47. Finding Excess Practice • 15.0 g of potassium reacts with 15.0 g of iodine. 2 K + I2 2 KI • We found that Iodine is the limiting reactant, and 19.6 g of potassium iodide are produced. 15.0 g I2 1 mol I2 2 mol K 39.1 g K 254 g I2 1 mol I2 1 mol K = 4.62 g K USED! 15.0 g K – 4.62 g K = 10.38 g K EXCESS Given amount of excess reactant Amount of excess reactant actually used Note that we started with the limiting reactant! Once you determine the LR, you should only start with it!

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