Module 4 Quiz

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William Rainey Harper College *

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Chemistry

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Feb 20, 2024

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CHM 110 Spring 2022 Module 4 Quiz Part 2 Name __Nimrah. I_________________________________________________________ By opening this document, you agree to complete this work independently and without the use of external resources including sites like Chegg or Course Hero, with the exception of the last part of question 1 (l) where you need to consult external sources to answer the question. Be sure to include a complete citation in APA or MLA format. Do not consult with any other people except me (you can ask me questions about the quiz prior to submitting your work). This quiz is cumulative over module 4. You have the option of submitting a draft of this quiz like you did with the previous module quizzes. You will then be able to make any modifications you feel are necessary based on my feedback and resubmit the quiz. Points are assigned following the final submission. You can also elect to only submit the final version. The first draft is due by Sunday, May 1. You can write answers to the questions that involve calculations or chemical symbols by hand. You must show your work for the quantitative problems to receive credit. You can take a picture or scan your answers. Please submit your answers as a single pdf (not a set of multiple pictures so insert the pictures into a word document and save that as a pdf). If you have the ability to write directly on the pdf version of this quiz, please do not cram your answers into the tiny spaces on this document. 1. Read the article How Lead Ended up In Flint’s Tap Water , by Michael Torrice published in the February 11, 2016, Chemical and Engineering News and answer the following questions. The article is included in Blackboard with this quiz. Click here to watch a video embedded in the article. a. The first contaminants the government told residents of Flint, MI were in their water were trihalomethanes, including CHClBr 2 and CHCl 3 . Draw Lewis structures for these two molecules. They each have a single central atom. CHClBr2: 4+1+7+7(2) = 26 H Br - C –Br Cl CHCl3: 4+1+7(3) = 26 Cl H - C - Cl: Cl .. : : .. .. .. : : .. : : .. .. .. : : .. 1

b. Explain why these molecules are soluble in water. CHCl3 is polar compound which is why it is soluble in water because water is highly polar. And CHClBr2 is a liquid that also evaporates in the air but also dissolves in water because it is a clear, colorless liquid. c. When Flint switched its water supply to the Flint River, officials failed to add a source of phosphate ions to the water. Why did this failure result in lead ions entering the water? Support your answer with evidence from the article. Environmental engineers say that if water pH drifts too low in the absence of orthophosphate, the water can start to leach high levels of lead from pipes. d. What does the Roman numeral in name lead(II) phosphate represent and why is the correct formula for lead (II) phosphate Pb 3 (PO 4 ) 2 ? An ion's positive charge is indicated by a roman numeral in parentheses after the element name, followed by the word ion. It is the correct formula because Pb is lead from the periodic table and phosphate is a polyatomic ion and they are both metal and nonmetal makes up ionic and we take the charge on lead and phosphate. Note: See the particulate level figures in the article showing a cross section of a lead pipe and an iron pipe for a visual that may assist you in answering (e) and (f) below. e. When an oxidant such as oxygen molecules react with the elemental iron, lead or copper in the pipes, the metals are oxidized. What happens to the metals when they are oxidized? What happens to the oxygen molecules when the metals are oxidized? Metal oxidation occurs when an ionic chemical reaction occurs on the surface of a metal while oxygen is present. Electrons move from the metal to the oxygen molecules in this process. Negative oxygen ions are then generated and penetrated into the metal, resulting in the formation of an oxide surface. f. Another problem in the Flint water distribution system was the growth of pathogens that resulted from the exposed iron metal in pipes reducing the free chlorine molecules. What happens to the chlorine molecules when they are reduced? What happens to the iron metal when it reduces the chlorine molecules? Chlorine rapidly changes dissolved iron to solid iron that will precipitate. Each chlorine atom gains one electron to form a chloride ion. g. What additional impact did the incorrect pH of the water have on lead ion levels? Explain. The pH drop over time seems to indicate that plant operators in Flint didn't even have a target pH as part of a corrosion plan. h. Did the water from the Flint water treatment plants need to be made more acidic or more basic to prevent the problem in (g)? Use evidence from the article to support your answer. More basic i. The Environmental Protection Agency (EPA) action level for Pb is 15 ppb. What does this mean and when is action required? It is the EPA Lead action plan. If 10 percent of the samples from these homes have water concentrations that are greater than the action level, then the system must perform actions such as public education and lead service line replacement. 2

j. What was the concentration of Pb in one of the Flint homes and how does that compare to the EPA action level? 252 homes and reported on their website, flintwaterstudy.org, that the city’s 90th percentile lead level was 25 ppb. EPA’s action limit is based on a 90th percentile calculation, meaning that if 10% of homes exceed the agency’s 15-ppb threshold, then action is required. k. Do you think it is possible for other communities to have a problem with lead in their drinking water? Why or why not? Yes, it can lead to different diseases in adults. l. This article was written in 2016; has the drinking water problem in Flint been resolved? Consult external sources to answer this question. Include complete citations for any references used. It does not seem like it has ended yet. 2. Answer the following questions based on the data in table 1. a. This table contains four sets of molecules whose molar masses are within two grams of each other so are considered the same size. Explain the differences in their boiling points for each pair (methane and water, ethane and methanol, propane and ethanol and butane and 1-propanol). In methane and water, the water has a strong hydrogen bond between the H2O molecules, in methane there is no hydrogen bond, it has very week interaction. In ethane and methanol, methanol has strong hydrogen bond and ethane doesn’t. In propane and ethanol, ethanol has strong hydrogen bonding. And 1- propanol has a stronger hydrogen bonding. Considering this, methane, ethane, propane, and butane are gasses and examples of hydrocarbon. Butane cannot form hydrogen bonds. b. What else has to be considered in order for the data in this table to support the claim that boiling point increases with the size of the molecule (with size measured by molar mass)? Explain. If the boiling point increases, the molar mass increases as well for the Alkanes. For alcohol, the molar mass increase so does the boiling point increases. c. Consider the two molecules C 5 H 12 and CH 3 CH 2 CH 2 CH 2 OH. i. The boiling point of one of these two molecules is 36 o C. Which one? Explain. Pentane is C5H12 has the boiling point of 36C. It cannot be 1- butanol because it is higher than 1- propanol as well as a higher amount of boiling point than 1- propanol. ii. Predict a reasonable value for the boiling point of the other molecule and explain the reasoning behind your prediction. The boiling point of compound depends on the interaction between molecules. In alcohol as there is presence of stronger interaction like hydrogen bonding they have higher boiling point in comparison to alkane. Table 1: Boiling Points of molecules. Molecule Name Molecular Formula Boiling point C° Molar mass (g/mol) Methane CH 4 -164 16 3

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Molecule Name Molecular Formula Boiling point C° Molar mass (g/mol) Water H 2 O 100 18 Ethane C 2 H 6 -89 30 Methanol CH 3 OH 65 32 Propane C 3 H 8 -42 44 Ethanol CH 3 CH 2 OH 78 46 Butane C 4 H 10 -1 58 1-propanol CH 3 CH 2 CH 2 OH 97 60 3. Prepare a concept map that includes 10 concepts from module 4. You can additional concepts from other modules but 10 must be key concepts from module 4. Consult the learning outcomes for Module 4 posted in Blackboard and module 4 in the text for ideas for the key concepts. 4. You will receive a bag of tea leaves in class that you will use to respond to this question. Place 250 mL (about 1 cup) of boiling water in a heat resistant mug. Add the tea bag containing Butterfly Pea Flower tea and let it steep for 5 minutes. Remove the tea bag and set it aside (it can be used again if you want to do a second trial). Allow the tea to cool for about 15 minutes so it is cool enough to touch. If you have two clear glasses, pour half of the tea into each of those glasses. One of the glasses will serve as your control. Since this is an experiment, do not allow anyone to drink the tea. It can be discarded down the drain when you are finished testing.  Record the initial color of the tea.  Add ½ teaspoon of vinegar (or juice from half a lemon) to the tea in one of the cups, stir and record your observations.  Sprinkle a small quantity of sodium bicarbonate (baking soda, NaHCO 3 ) to the same cup of tea to which you added the vinegar or lemon juice and stir. Continue until you observe a change. Record your observations.  If you have more vinegar or lemon juice, add it to the same cup of tea and record your observations. a. Share your observations (in a data table or with pictures). b. To what other substances in the acid base lab is the tea similar? Explain. c. Predict what you would observe if you added some sulfuric acid to the tea? Explain. 5. Self-Assessment: How do you rate the quality of your work on this assessment:  exemplary (A level work: learned the content and can apply it consistently to problems)  proficient (B level work: learned and can apply most of the content) 4