Note Taking Guide: Episode 701. Lab results: 1 doz grains of rice = g (Use this fact as a conversion factor.) Avogadro s Number - the = the number

Transcription

1 Note Taking Guide: Episode 701 Name Lab results: 1 doz grains of rice = g (Use this fact as a conversion factor.)? grains of rice = 1.94 g Avogadro s Number - the = the number Molar Mass the of one of any molar mass of an element (g/mol) equals the of the element in grams molar mass of a compound equals the of the of the making up the example problems: Find the molar masses ofmagnesium g/mol chlorine g/mol magnesium chloride g/mol Find the molar mass of aluminum oxide. 7.1

2 How many moles of atoms are there in 8.0 g of Mg? How many atoms are in 0.7 g of He? Work Problem Set #1 on back. more example problems: What would be the mass of 5.3 X formula units of calcium iodide? Episode 701 Problems: Fill in masses from lab data and solve. How many atoms are in grams of copper? 7.2

3 How many formula units are in grams of salt? How many molecules are in grams of water? The Chemistry Quiz CR1. CR

4 Problem Set One: Episode 701 How many atoms are in 3.5 grams of silicon? How many formula units are in 32.6 grams of potassium oxide? How many molecules are in 0.25 grams of dinitrogen pentoxide? 7.4

5 Worksheet: Mole Problems Name Part 1: Molar Mass Use the periodic table to find the molar masses of the following. HCl K 2 CO 3 Ca(OH) 2 Na 3 PO 4 Part 2: Mole Conversions Work each of the following problems. SHOW ALL WORK. 1. How many atoms are in 6.2 moles of aluminum? 2. Convert 5.3 x molecules of CO 2 to moles. 3. How many formula units of sodium acetate are in 0.87 moles of sodium acetate? 4. Convert 3.55 moles NaCl to formula units. 7.5

6 5. Convert 3.00 moles As 2 S 3 to grams. 6. How many moles are represented by 11.5 g of C 2 H 5 OH? 7. What is the mass of 9.30 moles of SiH 4? 8. Convert 8.00 x molecules of H 2 to moles. 9. How many atoms of tin are found in 3.50 moles of tin? 10. How many grams of tin are found in 3.50 moles of tin? Bonus: How many atoms of hydrogen are found in 12.6 moles of water? 7.6

7 Problems: Episode 701 How many atoms are in a sample of copper with a mass of grams? How many formula units are in a sample of salt with a mass of grams? How many molecules are in a sample of water with a mass of grams? 7.7

8 Practice: Mole Problems Name What is the mass in grams of moles of Mg? How many moles of atoms are there in g of sulfur? What is the mass of 24.6 formula units of magnesium oxide? How many molecules of dinitrogen pentoxide are contained in g of dinitrogen pentoxide? 7.8

9 What is the mass of 4.56 moles of sulfur dioxide? What is the mass of 4.56 molecules of sulfur dioxide? How many formula units are in g of Ca 3 (PO 4 ) 2? How many moles are in 1.5 x atoms of fluorine? What is the mass of 2.80 x molecules of CO 2? 7.9

10 Worksheet: More Mole Problems Name Work each of the following problems. SHOW ALL WORK. 1. How many atoms are contained in 3.46 moles of magnesium? 2. Convert g sodium carbonate to formula units. 3. What is the mass of 12.4 molecules of carbon tetrachloride? 4. How many moles are contained in 0.43 g Al 2 O 3? 5. The number of silicon atoms in 42.1 g of silicon is g of CuCl 2 = moles CuCl

11 7. Convert 2.76 g Se to moles Se. 8. What is the mass in grams of 9.31 x atoms of carbon? f.u. MgO = moles MgO 10. How many grams of sodium is equal to 6.92 x atoms of sodium? 11. The mass of 3.55 moles of NaCl is. BONUS What is the mass, in kilograms, of 2.46 x formula units of barium chloride? 7.11

12 Worksheet: Even More Mole Problems Name Work each of the following problems. SHOW ALL WORK. 1. How many grams are contained in 0.54 moles of calcium? 2. Convert 2.54 moles magnesium carbonate to formula units. 3. What is the mass of 3.1 x molecules of carbon monoxide? 4. How many formula units are contained in 0.67 g CaO? 5. The number of nitrogen molecules in 1.2 moles of N 2 is x f.u. of Al 2 O 3 = grams Al 2 O

13 7. Convert 3.1 moles of water to grams of water. 8. What is the mass in grams of 4.6 x molecules of carbon tetrabromide? x f.u. NaCl = grams NaCl 10. How many moles of silver is equal to 0.31 grams of silver? 11. The mass of 2.60 moles of SO 2 is. BONUS How many atoms of oxygen are contained in 12.3 kilograms of carbon dioxide? 7.13

14 Lab: % Sugar in Gum Datasheet Name Part 1 1. Mass the piece of gum inside the wrapper. 2. Open the piece of gum being certain to SAVE THE WRAPPER, and mass the gum by itself. 3. Chew the piece of gum until no more flavor is tasted. 4. Put the chewed piece of gum back on the wrapper. 5. Let the gum dry overnight. Part 2 1. After allowing the gum to dry overnight, mass the piece of gum on the wrapper. 2. Throw the gum and wrapper in the trashcan. Data mass of gum and wrapper before chewing mass of gum without wrapper mass of gum and wrapper after chewing Conclusions 1. The mass of the gum (decreases, increases) while being chewed because the sugar in the gum dissolves in the saliva in the mouth. Using the data, what is the mass of the sugar in the gum? 2. Calculate the percentage of sugar in the gum using the following equation. % sugar in gum = mass of sugar mass of gum! 100% 7.14

15 Note Taking Guide: Episode 702 Name Example Problem: Find the % by mass of oxygen in water. Percentage by mass of element in a compound = (mass of element in 1 mol of compound molar mass of compound ) x 100 % (after completing lab #1) Find the % of carbon in sodium bicarbonate (NaHCO 3 ). Find the % composition of aluminum oxide. (This means to find the % of each element in the compound.) 7.15

16 Empirical Formula: simplest number of in a Example Problem: Find the empirical formula for a compound containing 56.6g of K, 8.7g of C, and 34.7g of O. Step #1: Convert each mass into moles of the element. Step #2: Divide each by the smallest to find a simple whole number ratio. Ex. Problems: Work on separate sheet of paper. % Na % S % O (Hint: When % are given, assume you have 100g of the compound, and the % changes to grams.) P x O y g sample g P (Hint: After step 2, if the ratio is still not whole numbers, multiply both subscripts by a number, such as 2 to get rid of fractions, such as 0.5.) The Chemistry Quiz CR1. CR

17 Lab One: Episode 702 Datasheet Name I. Fill in the data table below as you watch the lab on the video. mass of sodium bicarbonate mass before reaction mass after reaction II. Write a balanced equation for the reaction that took place. (Hint: the narrator on the video will help you with this.) III. Conclusion Questions: Answer each question completely. SHOW ALL WORK! Calcuate the mass of carbon dioxide produced in the experiment. (Hint: Think about what bubbled away.) Use molar masses to calculate the percent of carbon in carbon dioxide using the following formula. mass of C % C in CO 2 =! 100% mass of CO

18 Calculate the mass of carbon in the sample of carbon dioxide using the same formula and your answers to the previous two calculations. Calculate the percentage of carbon that was in the original sample of sodium bicarbonate using the following formula. mass of C % C in NaHCO 3 =! 100% mass of NaHCO 3 IV. Practice Problems. SHOW ALL WORK! Calculate the percentage sodium in sodium oxide. Calculate the percentage aluminum in aluminum phosphate. Calculate the percentage hydrogen in hydrogen peroxide. Calculate the percentage nitrogen in dinitrogen pentoxide. 7.18

19 Lab Two: Episode 702 Datasheet Name I. Fill in the data table below as you watch the lab on the video. mass of empty test tube mass of test tube with copper oxide (before reaction) mass of test tube with copper (after reaction) II. Calculations: SHOW ALL WORK IN THE SPACE PROVIDED. Use the data to calculate the mass of copper oxide. Use the data to calculate the mass of copper. Use the two previous calculations to calculate the mass of the oxygen that was driven off. Using molar masses, calculate the moles of copper and oxygen. mass of copper oxide g mass of copper g mass of oxygen g moles of copper mol moles of oxygen mol 7.19

20 III. Conclusion Questions: Answer each question completely. SHOW ALL WORK! 1. Within bounds of experimental error, use the mole ratio to write the formula of the compound. 2. What is the name of this compound? (Hint: you need a Roman numeral in the name) 3. A compound of calcium and bromine is analyzed in the lab. A 20.0 g sample contains 4.00 g calcium. What is the empirical formula of the compound? 4. Find the empirical formula of a compound found to contain % potassium, % chromium, and the remainder oxygen. 7.20

21 Worksheet: % Composition and Empirical Formulas Name Part 1: % Composition Calculate the percent composition of the following compounds. SHOW ALL WORK. HCl K 2 CO 3 Part 2: Empirical Formulas Work each of the following problems. SHOW ALL WORK. 1. A compound is found to contain % iron and % sulfur. Find its empirical formula. 2. In the laboratory, a sample is found to contain 1.05 grams of nickel and 0.29 grams oxygen. Determine the empirical formula. 7.21

22 Practice: % Composition and Empirical Formulas Name Calculate the % composition for Mg(OH) 2. What is the empirical formula for a compound if a 2.50 g sample contains g of calcium and 1.60 g of chlorine? Calculate the % composition for potassium sulfate. A compound is 85.7 % carbon and 14.3 % hydrogen. Calculate the empirical formula. 7.22

23 Worksheet: More Practice with % Composition Name and Empirical Formulas Part 1: % Composition Calculate the percent composition of the following compounds. Ca(OH) 2 Na 3 PO 4 Part 2: Empirical Formulas Work each of the following problems. SHOW ALL WORK. 1. Determine the empirical formula of a compound containing % silver, 8.25 % nitrogen, and the remainder oxygen. 2. A compound is found to contain 63 % manganese, Mn, and 37 % oxygen. What is the compound s empirical formula? 7.23

24 Note Taking Guide: Episode 703 Name Molecular Formula represents the number of of each in the not necessary for necessary for The molecular formula for water is, and empirical formula is also. The molecular formula for hydrogen peroxide is, and empirical formula is. Example Problem The empirical formula for glucose is CH 2 O. a) If the molar mass is g/mole, find the molecular formula. b) If the molar mass is g/mole, find the molecular formula. Problem Set One (work on your own paper) empirical formula CH NO 2 C 3 H 8 molar mass g/mol g/mol g/mol Ex. Problem: Find the molecular formula for a compound with- g N g O molar mass g/mol 7.24

25 Hydrates with molecules adhering to the or Na 2 CO 3 H 2 O indicates molecules adhering to each of sodium carbonate mass of = mass of compound minus mass of compound Example Problems Determine the formula of hydrated barium chloride from this data: initial mass of hydrated compound = 1.373g mass after heating = 1.175g Determine the formula for the hydrate that is % CaSO 3 and % H 2 O. (work on back) The Chemistry Quiz CR1. CR

26 Problem Set One: Episode 703 empirical formula molar mass CH 26 g/mol NO g/mol C 3 H 8 44 g/mol 7.26

27 Lab: Episode 703 Datasheet Name Mass of empty pipet Mass of hydrate and pipet Mass after 1 st heating Mass after 2 nd heating Calculations: 1. Using the data, calculate the mass of the water driven off. 2. Using your answer to number 1, calculate the number of moles of water driven off. 3. Using the data, calculate the mass of the anhydrous salt. 7.27

28 4. Using your answer to number 3 and the fact that your anhydrous salt is copper (II) sulfate, calculate the number of moles of anhydrous salt. 5. Using your answers to numbers 2 and 4, determine the formula of the hydrate. Conclusions: 1. A hydrate is a crystal with molecules adhering to the ions or molecules. 2. Define anhydrous. 3. Write the formula for hydrated zinc sulfate with 7 molecules of water adhering to each formula unit of zinc sulfate. 7.28

29 Worksheet: Molecular Formulas and Hydrates Name 1. What is the molecular formula of the molecule that has an empirical formula of CH 2 O and a molar mass of g/mol? 2. What is the molecular formula of the molecule that has an empirical formula of CH 2 Cl and a molar mass of g/mol? 3. Determine the formula for the hydrate from the given information: a g Li 2 SiF 6, g H 2 O b % CaSO 3, 23.1 % H 2 O 7.29

30 Worksheet: More Molecular Formulas and Hydrates Name 1. The empirical formula of a compound is found to be P 2 O 5. Experiments show that the molar mass of the compound is g/mol. What is the molecular formula of the compound? 2. A compound has the following % composition % C, % H, and % O. If its molar mass is g/mol, what is its molecular formula? 3. What is the formula for a hydrate which consists of 90.7 % SrC 2 O 4 and 9.30 % H 2 O? 7.30

31 Review Sheet: Unit 7 Name Vocabulary: Fill in the blanks with the most appropriate term. is also called Avogadro s number. The mass of one mole of any pure substance is called the mass. For any element, this mass is equal to the atomic mass with the unit /. The formula of a compound is the simplest whole number ratio of atoms, while the formula of a compound represents the actual number of each atom in the compound. are compounds that crystallize from a water solution with water molecules clinging to the crystal particles. Problems: Work each of the following problems showing all work. These problems are representative of each type of problem worked in this unit. For more practice on a given type of problem, refer back to Note Taking Guides, worksheets, and quizzes. 1. Calculate the molar mass for ethane, C 2 H Convert 45 g Se to moles of Se. 3. Convert 4.77 x molecules of SO 2 to grams. CHEMISTRY : A Study of Matter 7.31

32 4. What is the percentage composition of sodium hydroxide, NaOH? 5. A compound is found to contain 63 % manganese, Mn, and 37 % oxygen. What is the compound s empirical formula? 6. What is the empirical formula for a substance if a g sample of it contains grams of nitrogen, grams of hydrogen, and grams of chlorine? 7. What is the molecular formula for a compound with an empirical formula of NO 2 and a molar mass of 92.0 g/mol? 8. What is the formula for a hydrate that contains 6.4 g CuSO 4 and 3.6 g H 2 0? CHEMISTRY : A Study of Matter 7.32