Question

1) Describe an example of each of the following that may be found of your kitchen: Explain how your choice falls into this category, and if there is a chemical name or symbol for it, provide that as well. Provide a photo of your example with your ID card in it. a) a compound b) a heterogeneous mixture c) an element (symbol) Moving to the Caves… Lechuguilla Caves specifically. Check out this picture of crystals of gypsum left behind in Lechuguilla Cave.(There is a man in that photo!) 2) Describe three physical properties of these crystals, explain how each may be measured 3) Describe a process that would cause a physical change to these crystals and explain how this describes a physical change. How would you cause it? 4) Research and find what the density of gypsum is. Using the density you find, and a given mass of 1.101 g, calculate the volume (in cm3) of the gypsum crystal shown below. Show all work. Gypsum crystal 2.856 mm thick from Brookville, Saline County, Kansas 2007/Roush_gypsum/Index.html 5) Suppose you had a gypsum crystal with a mass of 25.320 g & volume was 10.96 ml. Put both of these numbers into scientific notation and indicate how many significant figures are in each number. 6) Calculate the density of the crystal sample using the mass of 25.320 g & volume of 10.96 ml, report your answer to the correct number of significant figures. Explain how you determined the number of significant digits to report in this calculation. 7) Suppose your crystal's density is 2.312 g/cm3. Use conversion factors to convert this to mg/μl Show all your work and all your units throughout. Now to the doctor's office: 8) I have come to see you, the doctor, because I was feeling a bit ill. The first thing the nurse did was look at me and see I had a large growth in my neck. “Wow!” she said. “How long has this been going on?” “For a couple of months”, I replied. After going through a bunch of tests, I was diagnosed with a goiter. This problem was historically treated with seaweed and is caused by a deficiency of iodine in the diet. The doctor prescribes iodine tablets. You, as the nurse, are faced with deciding which bottle of iodine I need. The doctor says I need Iodine-127. The supply person has made a mistake and put two different types of iodine on the shelf. I need Iodine-127. This is the heavier isotope of Iodine, the other being Iodine -126. a) Iodine is a diatomic element. Therefore, how would you represent elemental iodine in a chemical equation? Explain why you think it occurs in this way? b) Iodine-126 and Iodine-127 are isotopes of each other. Explain, in your own words, what an isotope is and write the complete chemical symbol for Iodine-126 and Iodine-127 and label what each number means. (this link will teach you how to write isotopic notation in word) c) What element do you think must have been present in seaweed to be a traditional therapy? ____________ 9) I have showed up at your office again. I still have the goiter so you ask me - “Have you been taking your iodine pills?” Being a little too well read, I decided to go to the health food store to buy some kelp to treat my goiter. I did this because I did not trust the identification capabilities of the staff. You want to assure me that you can identify any chemical in the stockroom. Below is a picture of one of the shelves. Type the correct name for each compound below the bottle. ___________________ _____________________ _________________ ___________________ _______________ ________________ 10) Some of the jars in the stockroom have been turned so that only the name can be seen. Type the formula for each of the following names. __________________________ __________________________ __________________________ __________________________ __________________________ __________________________ __________________________ __________________________ Now to the hospital? 11) I have checked into the hospital because I was feeling pretty sick and jittery. The first thing you did was ask me what I had done last night. “I went out with a couple of friends to a Chinese restaurant” I said. “Did you eat or drink anything strange?” you ask. “Just one cup of Chinese tea, and of course I have a one cup sample of it right here” You decided to send this one cup sample to the lab to have it analyzed. Below is the report sheet: Report: The tea was found to contain a large amount of the substance whose percent composition is given below: mass isolated from the cup: 1.53 grams percent composition: 49.49 % C; 6.48 % O; 5.19 % H; 28.86% N Molar Mass of compound; 194.16 g/mol a) From the information in the report, determine the empirical and molecular formula. Show all work. b) I am a chemistry teacher, and I ask you how many moles of the mysterious substance I ingested so I can tell my students. What would be your answer? c) I am also an extremely irritating patient, and I ask you how many molecules of this substance were in the tea sample. What would be your answer? 12) I have showed up at the hospital again. You are looking forward to hearing my new story! I have decided to take a new kind of baking soda, CaCO3 to control my blood pH. It reacts in my stomach, according to the following equation, and I feel bloated! ____ CaCO3(s) + ____HCl(aq) →_____H2O(l ) + ____CO2(g) + ___CaCl2(aq) a) Balance this equation by inserting the correct coefficients in red(even if they are the number one)in front of each reactant and product. b) You know from your physiology courses that I have 0.50 moles of hydrochloric acid in my stomach. I tell you I took 15 grams of the new baking soda. Calculate how many moles of carbon dioxide each reactant will make, then decide which compound will limit the amount of carbon dioxide produced. Show your work to back up your answer. c) Based upon your answer from part b) above, how many grams of carbon dioxide could have been made in my belly? d) You told me to burp into a bag and I will feel better. I ended up burping 5.86 grams of carbon dioxide. This is how much carbon dioxide was actually made in my belly. What is the percent yield for the above reaction? Show all work. Now to the ocean! I was scuba diving and gazed around at the underwater world, remembering that the ocean was just a huge solution, filled with solutes. 13) Give an example of a solute present in ocean water. Explain what a “solute” is in your answer and how your example fulfills this requirement. 14) Welding is be done in the ocean water! Many times, as welding occurs, a cloudy substance would form around the area. Welding uses a compound that has lead(II) nitrate in it. I knew that ocean water has sodium chloride in it. a) Type the balanced molecular equation for the formation of the cloudy material, including all phase labels. b) Type the complete and net ionic equation for the formation of this cloudy material. 15) I also remembered from general chemistry that there was gold in the ocean. If a very small amount was floating around in the form of Gold(I) sulfate, maybe I could use the principle of oxidation-reduction to recover it? a) Choose a metal from the activity series, that will replace gold from gold(I) sulfate to elemental gold and write a balanced reaction to illustrate this transformation, including all phase labels b) Determine the oxidation number of each element and write it below each-reactant and product in your molecular equation above. c) Identify which reactant has been oxidized and which reactant has been reduced. Explain how could you tell? 16) In chemistry class we also studied concentration. We took a 100-mL sample of ocean water and evaporated it to dryness. The result was 3.00 grams of NaCl and 2.00 grams of MgCl2. a) Give the individual balanced equation for the dissolving of MgCl2 in water to form ions, including phase labels. b) What is the concentration, in molarity, of only the magnesium ion (Mg+2), in the 100-ml sample,? 17) I also remembered using a “titration” to determine concentrations. I knew about acid-base titrations, but what about ions? I knew there was also chloride in the ocean. Could I recover it with titration…Consider the following: AgNO3( )+ MgCl2( ) + NaCl( )→AgCl( )+Mg(NO3)2( ) + NaNO3( ) a) Fill in the phase labels for each reactant and product above and balance the equation. Put your phase labels in bold and your coefficients in bold. b) I took another 100.0 ml sample of seawater, which contained the salts listed in the reactants and titrated them with silver nitrate. I isolated 13.63 grams of silver chloride. What must have been the molarity of the chloride ions in my seawater sample. To the past? 18) Alcohol baths used to be used to decrease the body temperature of a person with a fever. This was done by rubbing the person down with alcohol. a) Explain this use of alcohol given the following thermochemical equation; C2H5OH(l) → C2H5OH(g) ΔHo = 42.2 kJ/mol b) If a person is rubbed down with 250mL of alcohol and it all evaporates, how much heat exchange is occurring? (Density of alcohol is 0.786 g/mL at 20oC.) c) Viewing the alcohol liquid as the system, what was the initial volume of gaseous alcohol? d) If the final volume of gaseous alcohol after evaporation was 4.85 L Calculate the work done(in your town using the pressure on the day you used completed this exam- cite source) as the alcohol vapor expanded into the environment e) From this information, calculate the change in internal energy(E) for the “system” we defined above. Is it positive or negative? What does this mean? What is the system in this example? f) What would happen to the energy of the surroundings? What is the surroundings in this case? 19) The combustion of magnesium used to be used in flash bulbs because of the brightness of its flash. What is the heat of combustion of magnesium anyway? a) To determine the heat of combustion, I burned a 0.532 g sample of magnesium in a constant volume bomb calorimeter and the temperature of the water increased by 6.318 oC. Calculate the heat of combustion of my sample of Mg, in kJ/mol, given that the heat capacity of the calorimeter is 2085 J/ oC. b) Given the combustion of magnesium can be represented as Mg(s) + ½ O2(g) → MgO(s) Calculate the heat of combustion of magnesium from Appendix C in your text. Show all work. Compare to your previous answer Let There be Light! 20) How is the second defined? It is 9,192,631,770 cycles of radiation in the cesium atom. Calculate the wavelength of this radiation and indicate which region of the electromagnetic spectrum this wavelength found? Is this visible to our eyes? Explain. 21) Can You See a Single Photon? The wavelength corresponding to the maximum sensitivity of the human eye is 510 nm, the limit of sensitivity of the dark-adapted eye has been shown to correspond to a 100 ms flash of light of total energy 240 eV. (Little Shop of Physics- Colorado State University)(1 J = 6.241509 x 1018 eV) a) What is the energy of a single photon at this wavelength? b) How many photons does the flash contain? c) If 60% of the incident light is lost to reflection and absorption by tissues of the eye, determine how many photons reach the retina and if you can see a single photon? 22) Describe the Bohr theory of the hydrogen atom and how it explains the line spectrum of hydrogen. 23) What is the energy and wavelength of the photon of energy that was emitted by hydrogen if one of its electrons dropped from the n=6 state to the n=2 state. In what region of the electromagnetic spectrum does this wavelength fall? Which color line is this in the line spectra of hydrogen? 24) We have been talking about electrons, which are particles, behaving like waves. Your book discusses how X-ray diffractions provided evidence of this. Find an image that shows the diffraction of electrons, insert that here, and explain how this proves it is behaving like a wave. Cite sources. 25) What is the wavelength(in meters) of an electron moving at 2.20 x 106 m/s. What is the relationship between wavelength of a particle and its velocity? What region of the electromagnetic spectrum does this electron's wavelength fall? 26) The electron configurations of an “excited” atom is given below. Identify the atom, write its ground-state electron configuration, and give the orbital diagrams for the ground-state. [Ar]4s13d104p4 27) The electron configuration of a neutral atom in the ground state is 1s22s22p63s2.Write a complete set of quantum numbers for each of the electrons and name the element.

Answer 1