3Policies and Procedures - Test Corrections- Pink Sheets & Late Work- Notes & Practice Problems
4Chapter 8 BEAT SheetCalculate the percent composition of any element in a compoundDetermine the empirical formula of a compound given its percent compositionDetermine the molecular formula of a compound given its percent composition andmolar massDetermine the empirical formula of a hydrate from lab dataPerform mole road calculations to determine atoms, molecules, ions, mass, or molesfrom relevant dataDescribe the labs you performed this unit and what the key concept/learning was fromeach lab
5We have talked about this What is a mole?We have talked about this6.02 X 1023 times!
6What is a mole?A mole is the base unit used to measure the amount of a substance, abbreviated mol. One mol of anything is equal to x 1023 pieces of that thing.
7Mole Practice1. How many moles in 5.4 x 1020 atoms of Pb?
8Mole Practice2. How many atoms in 3.5 moles of Ag?
9Mole Practice3. How many total molecules in 1 mole of glucose: C6H12O6?
10Molecular and Formula Weight Last semester we learned about molecular weight and touched on formula weight. It is important to remember that a single atom’s weight in amu is the same as one mole of that atom in grams.Example: The weight of a single atom of aluminum is grams. Therefore 1mol of Al weighs grams.
11Molecular and Formula Weight This is known as the atomic mass: the mass of 1 mole of atoms of any element. This is the number that’s on the periodic table. But atoms are rarely by themselves—they are usually in compounds.How do you find the mass of a mole of a compound??
12Molecular and Formula Weight Example:Find the molecular mass of CO2C: 1 x = gO: 2 x = gg
13Molecular and Formula Weight Example:Find the formula mass of (NH4)CO3N: 1 x = gH: 4 x = gC: 1 x = gO: 3 x = gg
14Molecular and Formula Weight Practice Problems 4. Find the molecular mass of C6H12O6
15Molecular and Formula Weight Practice Problems 5. Find the molecular mass of dinitrogen pentaoxide
16Molecular and Formula Weight Practice Problems 6. Find the Formula mass of Na2SO4
17Molecular and Formula Weight Practice Problems 7. Find the Formula mass of potassium phosphate
18Molar Mass of a Substance When trying to find the mass of one mole of a substance we will make life easier by just referring to the molar mass of a material. It can be an atom, a molecule, or an ionic compound. We use the same technique to calculate the mass of a mole of O2, Pb, CH4, or NaCl.
19Molar Mass Practice Problems 8. Find the molar mass of O2
20Molar Mass Practice Problems 9. Find the molar mass of Pb
21Molar Mass Practice Problems 10. Find the molar mass of CH4
22Molar Mass Practice Problems 11. Find the molar mass of NaCl
23Molar Mass Practice Problems 12. When do you use atomic mass, molecular weight, and formula weight to find the molar mass?
24Molar Mass ConversionSince molar mass gives you the amount of grams in one mole of a substance you can use the molar mass to convert from grams to moles or vice versa.
25 56.8 𝑔 𝑀𝑛𝑂2 1 1 𝑚𝑜𝑙 𝑀𝑛𝑂2 86.9368 𝑔 𝑀𝑛𝑂2 = .653 𝑚𝑜𝑙 𝑀𝑛𝑂2 Molar Mass ConversionExamples:How many moles in 56.8 g of MnO2? 𝑔 𝑀𝑛𝑂 𝑚𝑜𝑙 𝑀𝑛𝑂 𝑔 𝑀𝑛𝑂2 = .653 𝑚𝑜𝑙 𝑀𝑛𝑂2
26Molar Mass Conversion Examples: How many grams in 3.4 moles of C6H6? 3.4 𝑚𝑜𝑙 𝐶6𝐻 𝑔 𝐶6𝐻6 1 𝑚𝑜𝑙 𝐶6𝐻6 =260 𝑔 𝐶6𝐻6
27Molar Mass Conversion Practice Problems 13. How many moles are in g of HNO3
28Molar Mass Conversion Practice Problems 14. How many moles are in 19.5 grams of NaCl
29Molar Mass Conversion Practice Problems 15. How many grams are in 15 mols of AlPO4
30Molar Mass Conversion Practice Problems 16. How many grams are in 5.34 mols of KBr
31The Volume of a Mole of Gas Until this point we have only converted from mass to moles, but what happens when we convert from volume to moles?Describe how we can measure the mass of a solid substance: Describe how we can measure the mass of a liquid substance: Can we measure the mass of a gaseous substance?
32The Volume of a Mole of Gas When we convert from volume to moles or moles to volume we use a constant of 22.4 liters per mole. This constant tells us that one mole of a gas has a volume of 22.4 liters. When using this constant we assume the gas is at STP (standard temperature and pressure) which is 1 atm and 0C
33The Volume of a Mole of Gas Also remember that if there is one mole of a sample of gas, that sample must have 6.02 x 1023 atoms in it!But since gases have different masses than their solid form, one mole of a gas does not weigh the same as its solid state!
34The Volume of a Mole of Gas Example:If the density of a gas is 2.3 g/L, what is its molar mass?2.3 𝑔 1 𝐿 𝐿 1 𝑚𝑜𝑙 =51.52 𝑔/𝑚𝑜𝑙
35The Volume of a Mole of Gas Example:What is the density of F2 at STP?
36The Volume of a Mole of Gas Practice Problems 17. Since we know that the gaseous state of a substance does not have the same mass as the solid state of the same substance, what can we say about the density of the two?
37The Volume of a Mole of Gas Practice Problems 18. How many moles are in 22.4 Liters of O(gas)?
38The Volume of a Mole of Gas Practice Problems 19. How many milliliters of Neon gas are in 2 mols?
39The Volume of a Mole of Gas Practice Problems 20. What is the molar mass of a gas that has a density of g/L? Which diatomic gas do you think it is?
40The Volume of a Mole of Gas Practice Problems 21. What is the density of Cl2 at STP?
42Mole Conversion Practice Problems 22. How many moles in 9.0 liters of a gas at STP?
43Mole Conversion Practice Problems 23. How many moles in 15 g of NaOH?
44Mole Conversion Practice Problems 24. How many liters would 2.9 moles of CO2 occupy at STP?
45Mole Conversion Practice Problems 25. How many grams would 30 L of CO2 gas weigh?
46Mole Conversion Practice Problems 26. How many atoms are in 50 L of H2 gas?
47Calculating Percent Composition Percent Composition is the percent by mass of each element in a compound. You find the percent composition by dividing the mass of the element by the total mass of the molecule.If you think back to the separation lab we have done this already by calculating the % of salt, % of sand, and % of iron!!
48Calculating Percent Composition Example:How many students are in this class? Find the percentage of Males and the percentage of Females.
49Calculating Percent Composition Example:What percentage of students in the class are 15? 16? 17?
50Calculating Percent Composition Example:What is the percent composition of each element in C6H12O6?
51Calculating Percent Composition Example:What is the percent by mass of each element in H2O?
52Calculating Percent Composition Example:How many grams of nitrogen are in 59 g of AgNO3?
53Percent Composition Practice Problems 27. Which compound has the smallest percentage of Chlorine?HClKClLiClNaCl
54Percent Composition Practice Problems 28. Of the following compounds, which does Strontium have the highest percent composition?SrCl2SrI2SrOSrS
55Percent Composition Practice Problems 29. What is the percent composition of Oxygen in the compound propanal (CH3CH2CHO)?
56Percent Composition Practice Problems 30. What is the percent by mass of Oxygen in H2SO4?
57Percent Composition Practice Problems 31. What is the total mass of oxygen in 1.00 mol of Al2(CrO4)3?
58Percent Composition Practice Problems 32. What is the percent composition of Carbon in CO?
59Calculation Empirical Formulas An empirical formula is the lowest whole number ratio of the atoms of the elements in a compound. The empirical formula may or may not be the same as the molecular formula.
60Calculation Empirical Formulas Example:The molecular formula for CO2 is the same as the empirical formula for CO2 because the atoms are in the lowest whole number ratio.
61Calculation Empirical Formulas Example:The molecular formula for C2H2, could be that, or it could be C6H6. But the empirical formula for both is CH, since that is the lowest whole number ratio.
62Calculation Empirical Formulas It is important to understand that the empirical formula gives you an idea of the ratio of between elements within a compound.
63Calculation Empirical Formulas Example:Calculate the empirical formula of a compound made up of:32.00% C42.66% O18.67 % N6.67% H
64Calculation Empirical Formulas Practice Problems 33. A compound contains 40% calcium, 12% carbon, 48% oxygen by mass. What is the empirical formula for this compound?
65Calculation Empirical Formulas Practice Problems 34. Write the empirical formula for the following compound: P4O10
66Calculation Empirical Formulas Practice Problems 35. A compound is 86% carbon and 14% hydrogen by mass. What is the empirical formula for the compound?
67Calculation Empirical Formulas Practice Problems 36. Which of the following is an empirical compound?C4H10C6H12O6P2O5C2H2O2
68Calculation Empirical Formulas Practice Problems 37. A compound was analyzed and was found to contain 75% carbon and 25% hydrogen by mass. What is the compounds empirical formula?
69Calculation Empirical Formulas Practice Problems 38. What is the simplest ration of nitrogen to oxygen in the compound nitrogen (IV) oxide
70Calculation Molecular Formulas Knowing that the Molecular formula of a substance is not always equal to the Empirical Formula of the substance, what can we say about Molecular Weight vs Empirical Formula Weight?
71Calculation Molecular Formulas We can determine the molecular formula we first know the molar mass and the empirical formula of the substance. We then compare the molar mass to the Empirical Formula Weight to determine the ratio.
72Calculation Molecular Formulas Examples: The molar mass of a substance is 60g and its empirical formula is CH4N. Find the Molecular Formula.
73Calculation Molecular Formulas Examples:The molar mass of a substance is 78g and its empirical formula is CH. Find the Molecular Formula.
74Calculation Molecular Formulas Examples:Find the molecular formula for a compound that has:54.5% C13.6% H31.8 % Nmolar mass = 88g
75Calculation Molecular Formulas Practice Problems 39. What’s the molecular formula of a compound given the empirical formula P2O5 and molar mass 284 g?
76Calculation Molecular Formulas Practice Problems 41. What is the molecular formula of a compound that has a molecular mass of 42 g and empirical formula of CH2?
77Calculation Molecular Formulas Practice Problems 42. Find the molecular formula for a compound that has:54.5% C13.6% O31.8 % Nmolar mass = 176 g/mol
78Calculation Molecular Formulas Practice Problems 43. Find the molecular formula for a compound that has:25.9% N74.1% Hmolar mass = 108 g/mol
79Calculation Molecular Formulas Practice Problems 44. Find the molecular formula for a compound that has:22.8 g Ba2.00 g C8.00 g Omolar mass = g/mol
80HydratesHydrated compounds have water molecules attached to them. CuSO45H2O is copper (II) sulfate pentahydrate. For every formula unit of CuSO4, there are 5 water molecules attached to it. There are always numerous waters for one salt.
81HydratesExample:Start with 1.54 g wet magnesium phosphate. Dry it so that there are only 1.28 g residue left. Find the formula of the hydrate.
82HydratesExample:Calculate the percent composition in NaCl ∙ 5H2O?
83Hydrates Practice Problems 45. Calculate the percent composition in BaCl2 ∙ 2H2O
84Hydrates Practice Problems 46. What is the percent by mass of the water in the hydrateNa2CO3 ∙ 10H2O?
85Hydrates Practice Problems 47. If you start with 1.54 g wet magnesium phosphate. Dry it so that there are only 1.02 g residue left. Find the formula of the hydrate.
86Hydrates Practice Problems 48. Start with 1.62 g of hydrated cobalt (II) chloride. After heating, there are 0.88 g of solid reside. Find the formula of the hydrate.