1. The bond in fluorine has a length of 133pm. a. b. c. d. Draw the Lewis Structure. Convert to meters. Convert to nm. What is the shape and bond angle? If you didn’t take the Bonding Test last week… they are in the testing center. You have ONE week (1/24) Or the score becomes a zero! Get into groups of 3. Take turns leading the group through the questions. Write a list of new vocabulary terms in your CB. Take 15 minutes to finish the activity. Find another group that has the same empirical formula as your Lego molecule. (The match is worth points!) When you finish, work on the Formula packet… you know more than you think you know! 1. 1. 1. What is the difference between an empirical formula and a molecular formula? Do you have questions on the front side of the activity? How did you find the total mass of your compound? 4. How did you calculate the percent composition of an element in a compound? Example: What is the percent composition of each element in sodium sulfate. 4. Were you able to find the bag containing empirical and molecular formulas that match? What can we say about the mass of a molecular formula compared to that of the empirical formula? Example: What is the molecular formula of a compound with a molar mass of 64.20 g/mol if the empirical formula is carbon tetrahydride (methane). You should be able to do … Pages 1 and 2- Determine the formula, calc % comp and answer the questions. Page 3- If you are having trouble with these…. Try page 4 (a little easier). Do the prelab and read the background. Honestly…. Do we know the formula for zinc chloride? So, we really aren’t “determining” the formula as much as we are “confirming” the formula. 1. 2. 1. You are going to mass the zinc. When it undergoes a chemical reaction, will the mass of Zn change? What does HCl look like when it is in aqueous solution? Discuss the reaction Zn + HCl You have about 7 minutes to get into groups and look at your Mole Review WS to find silly mistakes. (Please start looking on the back side!) The average score on this assignment in periods 4 and 8 was a “5/10”. You have a 250.0 g sample of nitrogen monoxide that undergoes a decomposition reaction. a. Determine the percent composition of each element. b. What is the mass of nitrogen? c. What is the mass of oxygen? Example: A compound has 45.0g of oxygen, 22.6g of sulfur and 32.4g of sodium. What is the empirical formula. Remember- the formula compares the number of MOLES… so we need to look at moles! Assume 100.g An oxide of aluminum is formed by the reaction of 4.151g Al with 3.692g of Oxygen. Determine the empirical formula of the compound. 1 6 I put the balances in the same locations that they were in on Wed… Why is that important? Sources of experimental error??? Work on the lab calculations as a group. No lone rangers… if you are strong, there may be someone in your group who needs you! Don’t rely on the smarty party in your group to do all the calculations… you would be amazed at how often they get things wrong. Be sure to read the entire question and answer all parts of the question! Look at your zinc chloride lab… 1. Did you do the prelab questions? 2. Do your calculations have the correct number of significant figures? 3. Did your error analysis answers have complete sentences? 4. Did you write a conclusion without personal pronouns? About 10 minutes A Hydrate is a compound that contains water. The chemical state of the water varies… In ionic compounds Na2SO4 ·10H2O Name: Sodium sulfate decahydride How would we calculate the molar mass! Is the ionic salt left when all the water has been driven off a hydrate. Purpose: To determine the molecular formula for the sample hydrate. CuSO4 · __??_ H2O Equipment available: Test tubes Test tube clamp Bunsen burner Scale Hot pad Scoopula Hot glove 100 ml beaker. Matches Copper (II) Sulfate hydrate- You can use 0.3g 10 minutes1. 2. 3. 4. Write a procedure. Design a data table that will help you collect all the data. Discuss the calculations you will need to perform to complete the lab. What safety concerns do you have? Background- Find out more about hydrates and what is “trapping” or “attracting” the water. (Cite your resources) 2. Purpose- If, then, because statement 3. Procedure- Step by step, clearly written. 4. Materials List- Complete with correct spelling 5. Data- Preferably on a table 6. Analysis- Calculations (can hand write and scan) 7. Conclusion- What was learned (no personal pronouns). 8. Share with each other on Google Docs… 9. Turn it in to me through my website. 1. Formula/Reaction unit Let's take a look Mass of empty test tube _____g Mass of test tube and Copper (II) Sulfate _____g Mass of Copper (II) Sulfate before heating _____ g Mass of Copper (II) Sulfate after heating Mass of water released during heating _____ g _____ g Remember you are finding the ratio of Copper (II) sulfate molecules to water molecules. 1. 2. 2. 3. What is the percent composition of water found in sodium sulfide nonhydride? Na2S · 9H2O A 5.0g sample of barium chloride hydrate was heated and only 4.3g of the anhydrous salt remained. What percent water was in the hydrate? A 6.7g sample of Na2SO4·H2O is heated. How much anhydrous salt remains? A 5.0g sample of Cu(NO3)2 · nH2O is heated and 3.9 g of the anhydrous salt remains. What is the value for n? Turn them in! Combustion reactions usually involve a hydrocarbon and oxygen as the reactants and produce carbon dioxide, water and energy. Write the chemical equation— If we can measure the amount of products released in the combustion reaction… we can figure out the empirical formula for the hydrocarbon. What is the empirical formula for the hydrocarbon that produces: 23.118 g CO2 18.930 g H2O C? H ? Consider the formula NaNO3 a. Draw the Lewis structures for Na and NO3. b. Label the cation and anion… do you see why they want to gain and lose electrons? c. Name the compound CH2 2. CH 3. C3H7 4. C2H3 1. Questions??