2. Chapter 7 Chemical Quantities or

3. How you measure how much? You can measure mass, volume, or you can count pieces of a substance. We measure mass in grams. We measure volume in liters. We count pieces in MOLES. No, not that kind of mole!!!

4. Moles Defined as the number of carbon atoms in exactly 12 grams of carbon-12. 1 mole is 6.02 x 10 23 particles. Treat it like a very large dozen 6.02 x 10 23 is called Avogadro's number. The units of Avogadro’s number can be whatever particle you are counting. – Examples: atoms, molecules, ions, etc… – In chemistry these are called Representative Particles

5. What are Representative Particles? The smallest pieces of a substance. For an element it is an atom. – Unless it is diatomic For a covalent compound it is a molecule. For an ionic compound it is a formula unit.

6. How do We Use Moles? Moles are used as conversion factors. This means they are used to change units. Remember, when solving using conversion factors there are 3 questions you want to ask yourself: – What unit do you want to get rid of? – Where does it go to cancel out? – What can you change it into?

7. Calculation question 1 How many molecules of CO 2 are the in 4.56 moles of CO 2 ? Answer: 2.75 x 10 24 molecules of CO 2

8. Calculation question 2 How many moles of water is 5.87 x 10 22 molecules? ANSWER: 0.0975 moles of water

9. Calculation question 3 How many molecules are there in 1.23 moles of C 6 H 12 O 6 ?

10. Measuring Moles The atomic mass unit (amu) is one twelfth the mass of a carbon 12 atom. Since the mole is the number of atoms in 12 grams of carbon-12, the decimal number on the periodic table is: – The mass of the average atom in amu This mass is equivalent to the mass of 1 mole of those atoms in grams.

11. Gram Atomic Mass The mass of 1 mole of an element in grams. 12.01 grams of carbon has the same number of pieces as 1.008 grams of hydrogen and 55.85 grams of iron. We can write this as 12.01 g C = 1 mole We can count things by weighing them.

12. Examples How much would 2.34 moles of carbon weigh? 28.1 grams of C How many moles of magnesium in 4.61 g of Mg? 0.190 moles of Mg

13. What about compounds? In 1 mole of H 2 O molecules there are two moles of H atoms and 1 mole of O atoms To find the mass of one mole of a compound: – Determine the moles of the elements they have – Find out how much their mass is by using the periodic table and then add them up

14. Example What is the mass of one mole of CH 4 ? 1 mole of C = 12.01 g 4 mole of H x 1.01 g = 4.04g 1 mole CH 4 = 12.01 + 4.04 = 16.05g

15. What is the molar mass of Fe 2 O 3 ? 2 moles of Fe x 55.85 g/mol = 111.70 g/mol 3 moles of O x 16.00 g/mol = 48.00 g/mol 111.70 g/mol + 48.00 g/mol = 159.70g/mol

16. Molar Mass The generic term for the mass of one mole. The same as gram molecular mass, gram formula mass, and gram atomic mass. This is the term we will be using in class. I do NOT weigh that much! The balance must be lying!!!

17. Examples Calculate the molar mass of the following: Na 2 S N 2 O 4 C Ca(NO 3 ) 2 C 6 H 12 O 6 (NH 4 ) 3 PO 4 78.05 g/mol 92.02 g/mol 12.01 g/mol 164.10 g/mol 149.12 g/mol 180.18 g/mol

18. Using Molar Mass Finding moles of compounds Counting pieces by weighing

19. Molar Mass The number of grams in 1 mole of atoms, formula units, or molecules. We can make conversion factors from these. It will allow us to change grams of a compound to moles of a compound. Or moles to grams

20. For example How many moles is 5.69 g of NaOH?

21. For example How many moles is 5.69 g of NaOH?

22. For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH

23. For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH l 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g

24. For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH l 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g add these together to get the molar mass – use it to convert! l 1 mole NaOH = 40.00 g

25. For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH l 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g l 1 mole NaOH = 40.00 g

26. For example How many moles is 5.69 g of NaOH? l need to change grams to moles for NaOH l 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g l 1 mole NaOH = 40.00 g

27. Examples How many moles is 4.56 g of CO 2 ? How many grams is 9.87 moles of H 2 O? 0.104 mol CO 2 177.86 g H 2 O

28. Gases and the Mole Where is my air tank?? I hope it’s filled to 22.4 L

29. Gases Many of the chemicals we deal with are gases. They are difficult to weigh, so we’ll measure volume We still need to know how many moles of gas we have. Two things affect the volume of a gas Temperature and pressure So we have to compare at the SAME temp. and pressure.

30. Standard Temperature and Pressure Avogadro's Hypothesis - at the same temperature and pressure equal volumes of gas have the same number of particles. 0ºC and 1 atm pressure abbreviated STP At STP 1 mole of gas occupies 22.4 L Called the molar volume

31. Examples What is the volume of 4.59 mole of CO 2 gas at STP? How many moles is 5.67 L of O 2 at STP? What is the volume of 8.8g of CH 4 gas at STP? 102.8 L 0.253 mol 12.28 L

32. All the things we can change

33. We have learned how to change moles to grams moles to atoms moles to formula units moles to molecules moles to liters

34. Volume Molecules Atoms Representative Particles Mass PT Moles 6.02 x 10 23 22.4 L Count

35. Percent Composition Like all percents Part x 100 % whole Find the mass of each component, divide by the total mass.

36. Example Calculate the percent composition of a compound that is 29.0 g of Ag with 4.30 g of S. 87% Ag and 13% S

37. Getting it from the formula If we know the formula, assume you have 1 mole. Then you know the pieces and the whole. Add up the molar mass of the entire compound Divide the mass of each element in the formula by the molar mass of the compound Multiply by 100 to get the percent

38. Examples Calculate the percent composition of C 2 H 4. 86% C and 14% H Calculate the percent composition of aluminum carbonate Al 2 (CO 3 ) 3. 23% Al, 15% C, and 62% Oxygen

39. Empirical Formulas vs. Molecular Formulas

40. The empirical formula is the lowest whole number ratio of elements in a compound. The molecular formula the actual ratio of elements in a compound. The two can be the same. CH 2 empirical formula C 2 H 4 molecular formula C 3 H 6 molecular formula H 2 O both

41. Finding Empirical Formulas Just find the lowest whole number ratio C 6 H 12 O 6 =CH 2 O CH 4 N 2 =CH 4 N 2 It is not just the ratio of atoms, it is also the ratio of moles of elements.

42. Empirical Formula vs. Molecular Formula Determine if each of the following formulas are the empirical formula or molecular formula: – C 5 H 7 N 3 empirical formula – H 2 O 2 molecular formula – C 6 H 9 molecular formula – BrCl 2 empirical formula