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AP Chemistry Chapter 3 Chemical Quantities (The Mole)

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Presentation on theme: "AP Chemistry Chapter 3 Chemical Quantities (The Mole)"— Presentation transcript:

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2 AP Chemistry Chapter 3 Chemical Quantities (The Mole)

3 Amedeo Avogadro Hypothesis: Equal volumes of different gases at the same temperature and pressure contain equal numbers of particles. Amadeo Avogadro H 2 hydrogen CH 4 methane

4 The Mole 1 dozen = 1 gross = 1 ream = 1 mole = x There are exactly 12 grams of carbon-12 in one mole of carbon-12.

5 Avogadros Number 6.02 x is called Avogadros Number in honor of the Italian chemist Amedeo Avogadro ( ). Amadeo Avogadro I didnt discover it. Its just named after me!

6 The Mole (Quantities) 1 mole = atoms molecules formula units Molar mass Molar mass (periodic table) 22.4 L for a 6.02 x (elements) (nonmetals) (cation-anion) Mass: Volume: Representative Particles:

7 1. Convert 3.00 moles of ammonia, NH 3, to grams of ammonia.

8 1 mole NH 3 = ?? g NH 3 Conversion factor: 3.00 mol NH 3 x= g NH 3 You have to find molar mass. (Use Periodic Table) mol NH 3 g NH 3

9 17.04 g NH g NH 3 NH g 1.01 g x g g g = x 1 Molar mass of ammonia. 7 N H mole NH 3 = g NH 3

10 1. Convert 3.00 moles of ammonia, NH 3, to grams of ammonia. 1 mole NH 3 = g NH 3 Conversion factor: 3.00 mol NH 3 x= g NH 3 mol NH 3 g NH 3 NH x 1 x g g = g/mol On calculator: 3.00 x = Round to 3 sig. figs g NH 3

11 Ch. 7 (Calculating Chemical Quantities) g NH 3 1 mol NH x 1 x g g = g/mol 1. = 51.1 g NH 3

12 2.How many molecules of carbon dioxide are in 2.00 moles of CO 2 ?

13 2.How many molecules of carbon dioxide are in 2.00 moles of CO 2 ? 1 mole CO 2 = 6.02 x molecules CO 2 Conversion factor: 2.00 mol CO 2 x= molec. CO 2 1 mole = 6.02 x representative particles CO 2 is made of all nonmetals so rep. particles are molecules mol CO 2 molec. CO 2

14 2.How many molecules of carbon dioxide are in 2.00 moles of CO 2 ? 1 mole CO 2 = 6.02 x molecules CO 2 Conversion factor: 2.00 mol CO 2 x= molec. CO 2 mol CO 2 molec. CO x On calculator: 2.00 x (6.02 x ) = x Round to 3 sig. figs x molec. CO 2

15 Ch. 7 (Calculating Chemical Quantities) x molec. CO g NH 3 1 mol NH x 1 x g g = g/mol 1. = 51.1 g NH 3

16 3.How many moles of oxygen are in 44.8 L of oxygen, O 2 ? 1 mole O 2 = 22.4 L O 2 Conversion factor: 44.8 L O 2 x= moles O 2 1 mole = 22.4 L (for any STP) L O 2 mol O On calculator: 44.8 ÷ 22.4 = 2 Show to 3 sig. figs moles O 2

17 Ch. 7 (Calculating Chemical Quantities) 2.00 mol O x molec. CO g NH 3 1 mol NH x 1 x g g = g/mol 1. = 51.1 g NH 3

18 4. How many grams of lithium are in 3.50 moles of lithium? 1 mole Li = g Li Conversion factor: 3.50 mol Li x= g Li mol Li g Li On calculator: 3.50 x 6.94 = Round to 3 sig. figs g Li

19 The Mole (Quantities) 1 mole = atoms molecules formula units Molar mass Molar mass (periodic table) 22.4 L for a 6.02 x (elements) (nonmetals) (cation-anion) Mass: Volume: Representative Particles:

20 5. How many moles of lithium are in 18.2 grams of lithium? 1 mole Li = g Li Conversion factor: 18.2 g Li x= mol Li g Li mol Li On calculator: 18.2 ÷ 6.94 = Round to 3 sig. figs mol Li

21 Representative Particles: Using Avogadros Number 6. How many atoms of lithium are in 3.50 moles of lithium? 3.50 mol Li = atoms Li 1 mol Li 6.02 x atoms Li 2.11 x Use 6.02 x when looking for atoms, molecules, or formula units x

22 Representative Particles: Two-part problem 7. How many atoms of lithium are in 18.2 g of lithium? 18.2 g Li = atoms Li 1 mol Li 6.02 x atoms Li 1.58 x g Li1 mol Li (18.2)/6.94 x (6.02 x ) x x

23 %NaX 100 = g 7.86 g = % Na %ClX 100 = g g = % Cl 8. A sample of sodium chloride, (NaCl) commonly called table salt contains 7.86 g of sodium and g of chlorine. Find the % composition. Find total mass of NaCl 7.86 g g Total mass = g Take the mass of the element divided by total mass.

24 %CX 100 = g g = g C 3 H 8 C3H8C3H8C3H8C3H g1.01 g x g g = x % C %HX 100 = g 8.08 g = % H 9. Find the % composition of propane, (C 3 H 8 ). 6 C H 1.01

25 10. A 12.8 g sample of a gas contains 6.4 grams of sulfur and 6.4 grams of oxygen. What is the empirical formula for this gas?

26 Formulas molecular formula = (empirical formula) n where n = integer molecular formula = C 6 H 6 = (CH) 6 empirical formula = CH Empirical formula: the lowest whole number ratio of atoms in a compound. Molecular formula: the true number of atoms of each element in the formula of a compound.

27 Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: H2OH2O C 6 H 12 O 6 C 12 H 22 O 11 Empirical: H2OH2O CH 2 O C 12 H 22 O 11 All can be divided by 6

28 Empirical Formula Determination 1.Convert grams values to moles for each element. 2.Divide by lowest moles. 3.If necessary: Multiply each number by an integer to obtain all whole numbers.

29 6.4 g S = g S 1 mol S x mol S = 0.20 mol S 6.4 g O = 0.4 = 0.40 mol O g O 1 mol O x 10. A 12.8 g sample of a gas contains 6.4 grams of sulfur and 6.4 grams of oxygen. What is the empirical formula for this gas? 16 S O mol 2. Divide by lowest moles. 1. Convert to moles. 2 1 S O SO 2 Empirical Formula

30 3.2 g H = 1.01 g H 1 mol H x 3.16 mol H 19.4 g C = g C 1 mol C x 11. An unknown clear colorless liquid with no odor is analyzed and found to contain the following. Determine the empirical formula. 1 H O mol 2. Divide by lowest moles. 1. Convert to moles. 1 2 H C O Empirical Formula 3.2 % Hydrogen 19.4% Carbon 77.4% Oxygen Assume 100 g sample = 3.2 g H = 19.4 g C = 77.4 g O 77.4 g O = g O 1 mol O x 1.6 mol 3 6 C H 2 CO 3 = 3.2 mol H = 1.6 mol C = 4.8 mol O

31 %NaX 100 = g g = g NaClNaCl g35.45 g x g g = x % Na %OX 100 = g g = % Cl 8. A sample of sodium chloride, (NaCl) commonly called table salt contains 7.86 g of sodium and g of chlorine. Find the % composition. 11 Na Cl 35.45

32 The Mole (Quantities) 1 mole = atoms molecules formula units Molar mass Molar mass (periodic table) 22.4 L for a 6.02 x (elements) (nonmetals) (cation-anion) Mass: Volume: Representative Particles:


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