Good Day! 2/25/2016 Starter: How many Liters are in one mole of any gas? Starter: How many Liters are in one mole of any gas? Today we will be working on mole problems and if time learning about percent composition and empirical formula. Today we will be working on mole problems and if time learning about percent composition and empirical formula. Answer: 22.4 liters. Answer: 22.4 liters.

Link to Notes on the Mole. Link to Notes on the Mole. Link to Notes on the Mole. Link to Notes on the Mole.

Question #1 (moles  mass) What is the mass of 7.50 moles of sulfur dioxide, SO 2 ? S = 32.1 g/mol O = 16.0 g/mol 7.50 mol SO 2 = g SO 2 1 mol SO 2 g SO 2 g SO 2 X

7.50 mol SO 2 = g SO 2 1 mol SO 2 g SO 2 g SO 2 X 64.1 g SO g SO 2 SO g 16.0 g x g 32.1 g g = x 1

7.50 mol SO 2 = g SO 2 1 mol SO 2 g SO 2 g SO X 64.1 g SO g SO 2 SO g 16.0 g x g 32.1 g g = x 1 481

Question 2: (Mass  Moles) How many moles are there in g of potassium sulfate K 2 SO 4 ? K=39.1 g/mol; S=32.1 g/mol; O=16.0 g/mol g K 2 SO 4 = mol K 2 SO 4 g K 2 SO 4 1 mol K 2 SO 4 X

993.6 g K 2 SO 4 = mol K 2 SO 4 g K 2 SO 4 g K 2 SO 4 1 mol K 2 SO 4 X g = g K 2 SO g x g x g 78.2 g g g x

Question 3: (Moles  Molecules) How many molecules are there in 4.55 moles of nitrogen (N 2 )? 4.55 mol N 2 = molec. N 2 1 mol N 2 molec. N 2 molec. N 2 X 1 mole = 6.02 x molecules 6.02 x x 10 24

Good Day! 2/25/2016 Starter: How do you know what a substance is? (Like on CSI when they “Analyze” something, what are they doing?) Starter: How do you know what a substance is? (Like on CSI when they “Analyze” something, what are they doing?) Today we will be finishing the mole problems and learning about percent composition and empirical formula. Today we will be finishing the mole problems and learning about percent composition and empirical formula. Answer: the answer will come towards the end. Answer: the answer will come towards the end.

Question 4: (Moles  molecules  atoms) How many atoms of nitrogen, N, are there in 2.18 moles of nitrogen (N 2 )? 2.18 mol N 2 = atoms N 1 mol N 2 molec. N 2 molec. N 2 X 1 mole = 6.02 x molecules 6.02 x x molec. N 2 atoms N atoms N X 2

Question 5: (molecules  moles) How many moles are there in x molecules of carbon tetrachloride (CCl 4 )? x molec.CCl 4 = mol CCl 4 molec. CCl 4 molec. CCl 4 1 mol CCl 4 X 1 mole = 6.02 x molecules 6.02 x x

Question 6: (moles  volume) What is the volume occupied by 4.20 moles of oxygen gas (O 2 ) at STP? 4.20 mol O 2 = L O 2 1 mol O 2 L O 2 L O 2 X 1 mole = 22.4 L for

Question 7: (volume  moles) How many moles are there in 33.5 L of argon gas (Ar) at STP? 33.5 L Ar = mol Ar L Ar 1 mol Ar 1 mol Ar X 1 mole = 22.4 dm 3 for

Now a puzzling quesiton How do you know what a substance is? How do you know what a substance is? Like on CSI when they “Analyze” something, what are they doing? Like on CSI when they “Analyze” something, what are they doing?

Answer: Chemistry! Chemistry! More specifically, Percent composition, (we run it through a machine that tells them the percentage of each element that is in the compound.) More specifically, Percent composition, (we run it through a machine that tells them the percentage of each element that is in the compound.) Then they use those percentages to come up with the Empirical Formula. Then they use those percentages to come up with the Empirical Formula. So to better understand this, we will first learn how to calculate the % composition, So to better understand this, we will first learn how to calculate the % composition, Then we will later learn how to turn that into the formula of an unknown substance. Then we will later learn how to turn that into the formula of an unknown substance.

The Formula for % Comp. % Element = Mass of Element x 100 Mass of Compound

%N X 100 = 92.0 g 28.0 g = Question 8: (Percent composition) 92.0 g N 2 O g N 2 O 4 N2O4N2O4N2O4N2O g 16.0 g x g 28.0 g g = x % N %O X 100 = 92.0 g 64.0 g = 69.6 % O

?%O X 100 = g g = Question 9: (Percent composition) 29.6 % O ?%F= % 100% = 70.4 % F A sample of a compound that has a mass of g is analyzed. The sample is found to be made up of oxygen and fluorine only. Given that the sample contains g of oxygen, calculate the percentage composition of the compound. Alternative method: g – g = g F %F X 100 = g g = 70.4 % F

47.9 g Zn = g Zn 1 mol Zn x Question 10: (Empirical formula) mol Zn 52.1 g Cl = g Cl 1 mol Cl x 1.47 mol Cl = 1 = 2 ZnCl 2 Assume 100g sample. 30Zn65.39 Find the empirical formula of a compound, given that the compound is found to be: 47.9% zinc (Zn) and 52.1% chlorine (Cl) by mass. 47.9% zinc (Zn) and 52.1% chlorine (Cl) by mass. 17Cl35.45

For you homework. Find the percentage composition of the following: Find the percentage composition of the following: 1.You obtain a sample of Iron (III) Oxide commonly called rust. After analyzing the sample you determine that there is 28g of Iron and 12g of Oxygen. What is the percentage composition of Iron and Oxygen in the sample? 1.You obtain a sample of Iron (III) Oxide commonly called rust. After analyzing the sample you determine that there is 28g of Iron and 12g of Oxygen. What is the percentage composition of Iron and Oxygen in the sample? 2. A 39.0 g sample of a gas contains 18 g carbon and 21 g nitrogen. What is the empirical formula of this gas? 2. A 39.0 g sample of a gas contains 18 g carbon and 21 g nitrogen. What is the empirical formula of this gas? 3. A bottle is found in your garage which contains an unknown liquid. It has a distinct odor that seems somewhat familiar to you yet you still do not know what this liquid is so you send it to a lab to have it analyzed. The following results of the analysis are sent to you by mail. The substance contains 3. A bottle is found in your garage which contains an unknown liquid. It has a distinct odor that seems somewhat familiar to you yet you still do not know what this liquid is so you send it to a lab to have it analyzed. The following results of the analysis are sent to you by mail. The substance contains 52.2% Carbon, 13.0% Hydrogen, 34.8% Oxygen 52.2% Carbon, 13.0% Hydrogen, 34.8% Oxygen