1. X Chemistry Unit 7 The Mole Problem Solving involving Chemical Compounds

2. Vocab: Molar Mass- the mass of 1 mole of a substance  Equal to the atomic mass for elements  For a compound, the sum of the atomic masses for all the atoms in a compound  Units = grams/mole = g/mol Mole - the amount of substance that is equal to 6.02x10 23 particles of that substance

3. Vocab: Representative particle- the smallest particle of a substance; defined by the type of substance:  Element = atom  Covalent compound = molecule  Ionic compound = formula unit  Charged atom = ion

4. Vocab: Avogadro’s Number- the number of particles in 1 mole of any substance  Avogadro’s # = 6.02x10 23 Molar Volume- the volume of 1 mole of ANY gas at STP (Standard Temperature and Pressure = 0°C and 1atm),  22.4 Liters

5. What is a Mole? Amedeo Avogadro (Italian Mathematician)  used Carbon as the basis for the masses of the other elements  devised a counting relationship between grams and moles  1 mole = 6.02x10 23 atoms of any element  1 mole of carbon = 12.0 g Carbon (matches the atomic mass on the P.T.)

6. What is a Mole? (REAL WORLD EXAMPLE) Relationships:  1 dozen = 12 donuts just like 1 mole = 6.02x10 23 atoms BUT:  1 dozen feathers = 0.015 grams and  1 dozen bricks = 32,400 grams! Although the amount of particles is the same, the weight is not necessarily the same!!

7. What is a Mole? The mass of 1 mole of any element will be different than 1 mole of any other element!! What are the masses of 1 mole of the following elements?  Magnesium = 24.31 g/mol  Nitrogen = 14.01 g/mol These values come from the periodic table!!

8. One-mole Amounts

9. Determining Molar Mass for a Compound: 1. Write the symbols of the elements in the formula down the left hand side of the paper. 2. Count the number of each atom of each element present. 3. Multiply the number of each atom by the molar mass of the corresponding element from the periodic table rounded to the tenths place. 4. Sum the products from step 3. 5. The units on your final answer are g/mol (grams per mole).

10. Determining Molar Mass: Examples:  CO 2  (NH 4 ) 2 SO 4

11. Mole Conversions Moles! Mass Representative particles (atoms, molecules, formula units, ions) Mole Conversions Use molar mass ( __ grams / 1 mole) Use Avogadro’s # (6.02 x 10 23 particles per 1 mole)

12. Mole Conversions Always start with the number given in the problem  If mass appears anywhere in the problem, you must use molar mass as a conversion!  If particles (atoms, molecules, ions) appear anywhere in the problem, you must use Avogadro’s number as a conversion! Cross out units that cancel Stop when you get to the unit asked for in the problem!

13. Converting between Moles and Mass (Grams): Dimensional Analysis!! Use molar mass as conversion factor! Moles to grams: Grams to moles:

14. Converting between Moles and Mass: Examples: How many moles of CCl 4 are there in 523.4 g?

15. Converting between Moles and Mass : Examples: (cont.) How many grams of Na are there in 12.3 moles of Na?

16. Converting between Moles and Particles: Dimensional Analysis!! Use Avogadro’s number as conversion factor! Moles to particles: Particles to moles:

17. Conversions Between Moles & Particles: Use Avogadro’s Number!! Examples: How many atoms of carbon are contained in 0.230 moles of C?

18. Conversions Between Moles & Particles Examples: How many moles of sodium chloride are contained in 8.73 x 10 22 molecules (formula units) of NaCl?

19. Conversions Between Moles & Particles Challenge!! How many molecules of barium chloride are contained in 1.07 grams of barium chloride?

20. Vocab: Percent composition – mass of the part divided by mass of the whole times 100 Empirical Formula – the simplest whole number ratio of atoms in a compound Molecular Formula- the true whole number ratio of atoms in a compound

21. Percent Composition Problems: 2 types: 1. Using mass data about a specific sample to find percentage of each component in the sample (More specific) 2. Using a chemical formula to find percentage of each element in a compound (More general)

22. Percent Composition Problems: Type 1: (just like the separation of a mixture lab!!)  % of element or component in a specific sample

23. Percent Composition Problems: Examples: If 20.55 g of sodium combines completely with 31.75 g of chlorine to form a compound, what is the % composition of each element in this compound?

24. Percent Composition Problems: Type 2:  Mass of each element in 1 mole of a compound (1 mole  use the molar mass!!)

25. Percent Composition Problems: Example: What is the percent composition of each element in C 12 H 22 O 11 ?

26. Empirical Formula vs. Molecular Formula Molecular Formula P 3 H 6 C 6 H 12 O 6 N 6 F 8 Empirical Formula PH 2 CH 2 O N 3 F 4

27. Identify the following as empirical or molecular formulas  Ribose, C 5 H 10 O 5, a sugar molecule in RNA.  Ethyl butanoate, C 6 H 12 O 2, a compound with the odor of pineapple.  Chlorophyll, C 55 H 72 MgN 4 O 5, part of photosynthesis.  DEET, C 12 H 17 ON, an insect repellent.  Oxalic acid H 2 C 2 O 4, found in spinach and tea.