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Molar Relationships

Molar Relationships. Dozen = 12. Pair = 2. Names associated with an amount. Can you think of any more?????. The Mole…. The mole (mol) is the amount of a substance that contains as many elementary entities as there are atoms in exactly 12.00 grams of 12 C.

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Molar Relationships

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  1. Molar Relationships

  2. Dozen = 12 Pair = 2 Names associated with an amount Can you think of any more?????

  3. The Mole….. The mole (mol) is the amount of a substance that contains as many elementary entities as there are atoms in exactly 12.00 grams of 12C 1 mol = NA = 6.0221367 x 1023 Avogadro’s number (NA)

  4. What is the mass of one mole of: S C Hg Cu Fe 3.2

  5. Molar Mass • The Mass of 1 mole (in grams) • Equal to the numerical value of the average atomic mass (get from periodic table) 1 mole of C atoms = 1 mole of Cu atoms = 1 mole of S atoms = 1mole of Hg atoms = 1 mole of Fe atoms =

  6. Learning Check! Find the molar mass (usually we round to the tenths place) = 79.9 g/mole • 1 mole of Br atoms • 1 mole of Sn atoms = 118.7 g/mole

  7. 1S 32.07 amu 2O + 2 x 16.00 amu SO2 SO2 64.07 amu Molecular mass (or molecular weight) is the sum of the atomic masses (in amu) in a molecule. For any molecule molecular mass (amu) = molar mass (grams) 1 molecule SO2 = 64.07 amu 1 mole SO2 = 64.07 g SO2 Let’s try some more…………….. 3.3

  8. Molar Mass of Molecules and Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 = 111.1 g/mol 1 mole Ca x 40.1 g/mol + 2 moles Cl x 35.5 g/mol = 111.1 g/mol CaCl2 Practice with this one: 1 mole of N2O4=

  9. Learning Check! • Molar Mass of K2O = ? Grams/mole B. MolarMass of antacid Al(OH)3 = ? Grams/mole

  10. Learning Check Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass.

  11. So, if one mole = the formula mass how do we calculate…. The mass of 05 mol of Calcium Carbonate The mass of 2.25 mol of Sodium Chloride

  12. How many moles are there in? 100 g of Magnesium Hydroxide ? 64 g of Oxygen ?

  13. Converting to # of atoms or molecules How many atoms are in 3.00 moles of Iron? How many atoms are in 0.25 moles of Water?

  14. Molar Mass The molar mass of a compound is found by adding Together the molar masses of all of its elements, taking Into account the number of moles of each element present. Homework: pg 157 # 5-11

  15. Factor-Label Method (also called… dimensional analysis) Use fractions that include numbers and units to convert from one item to another. All fractions must have a valued of “1” Example problem: How many seconds are there in one year?

  16. Types of Mole Conversion Problems: Grams to Moles --- Moles to Grams Example Problem: How many Moles are in 58 g of NaHCO3? How many grams are in 3.75 Moles of Water?

  17. Moles Particles (atoms,ions,molecules) How many atoms are in .75 moles of Oxygen Gas? How many moles are in 2.709 x 1025 molecules of Calcium Hydroxide? How many hydroxide ions are there in 4.5 Moles of Calcium Hydroxide?

  18. Percent Composition • Percent Composition – • the percentage by mass of • each element in a compound Part _______ Percent = x 100% Whole So… Percent composition of a compound or = molecule Mass of element in 1 mol ____________________ x 100% Mass of 1 mol

  19. Percent Composition Example: What is the percent composition of Potassium Permanganate (KMnO4)? Molar Mass of KMnO4 K = 1(39.1) = 39.1 Mn = 1(54.9) = 54.9 O = 4(16.0) = 64.0 MM = 158 g

  20. Percent Composition Example: What is the percent composition of Potassium Permanganate (KMnO4)? Molar Mass of KMnO4 = 158 g 39.1 g K % K x 100 = 24.7 % 158 g 54.9 g Mn 34.8 % x 100 = % Mn 158 g K = 1(39.10) = 39.1 64.0 g O x 100 = 40.5 % % O Mn = 1(54.94) = 54.9 158 g O = 4(16.00) = 64.0 MM = 158

  21. Percent Composition Determine the percentage composition of sodium carbonate (Na2CO3)? Molar Mass Percent Composition 46.0 g x 100% = 43.4 % Na = 2(23.00) = 46.0 C = 1(12.01) = 12.0 O = 3(16.00) = 48.0 MM= 106 g % Na = 106 g 12.0 g x 100% = 11.3 % % C = 106 g 48.0 g x 100% = 45.3 % % O = 106 g

  22. Hydrates Hydrated salt – salt that has water molecules trapped within the crystal lattice Examples: CuSO4•5H2O , CuCl2•2H2O Anhydrous salt – salt without water molecules Examples: CuCl2 Can calculate the percentage of water in a hydrated salt.

  23. Hydrated Compounds: Chemicals that usually have water associated with them. How they are written: BaCl2. 2H2O – Barium Chloride dihydrate CuSO4.5H2O – Copper Sulfate pentahydrate NaCO3.10H2O-__________________

  24. Percent Composition If 145 grams of copper (II) sulfate pentahydrate is completely dehydrated, how many grams of anhydrous copper sulfate will remain? CuSO4.5 H2O 1. Molar Mass 2. % CuSO4 Cu = 1 x 63.55 = 63.55 g S = 1 x 32.06 = 32.06 g O = 4 x 16.00 = 64.00 g MM = 159.61 g 159.6 g X 100 = 63.92 % 249.7 g 3. Grams anhydrous CuSO4 H = 2 x 1.01 = 2.02 g O = 1 x 16.00 = 16.00 g MM = 18.02 g 0.6392 x 145 = 92.7 g Mass of 5 moles of H2O = 5 x 18.02 g = 90.1 g Total Molar mass = 159.6 g + 90.1 g = 249.7 g

  25. Calculate the Molar Mass of Hydrates-- ZnSO4.7H2O Na2CO3.10H2O

  26. Formulas Percent composition allow you to calculate the simplest ratio among the atoms found in compound. Empirical Formula – formula of a compound that expresses lowest whole number ratio of atoms. Molecular Formula – actual formula of a compound showing the number of atoms present Examples: C6H12O6 - molecular C4H10 - molecular - empirical - empirical C2H5 CH2O

  27. Determining Empirical Formula

  28. Try this one: An oxide of aluminum is formed by the reaction of 4.151 g of aluminum with 3.692g of oxygen. Calculate the empirical formula.

  29. A 4.550 g sample of cobalt reacts with 5.475 g chlorine to form a binary compound. Determine the empirical formula for this compound.

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