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Final Study Guide (Semester 2) Answer Key Chemstry / Bly Ch. 8 1. Consider this reaction: CuSO4(aq) + 2KOH(aq) Cu(OH)2(s ) + K2SO4(aq) Which compounds above are strong electrolytes? CuSO4 , KOH , K2SO4 a. Which chemical above is not soluble in water? Cu(OH)2 c. Which chemical above is the precipitate? Cu(OH)2 2. Solutions of Barium nitrate and potassium sulfate are mixed. ***The first thing you should do when solving this is look at the common ion chart and write down all the ions. It’s much easier than looking them up again for each question. a. Write the balanced molecular equation. Include phase symbols. Ba(NO3)2(aq) + K2SO4(aq) BaSO4(s) + 2KNO3 (aq) Switch the cations in the reactants to make two products that are new ionic compounds. If one of the products is not soluble (check the solubility chart p245—you can use this on the test), it is the precipitate. Write (s) on the insoluble chemical. Sometimes both are insoluble. b. Write the balanced complete ionic equation. Include phase symbols. Ba2+(aq) + 2NO32-(aq) + 2K+(aq) + SO42-(aq) BaSO4(s) +2NO32-(aq) + 2K+(aq) *Don’t forget the charges of the ions! c. List the spectator ions: NO32- K+ *The spectator ions are the ions that do not make a precipitate. *Don’t forget the charges when you write the spectator ions! d. Write the balanced net ionic equation. Include phase symbols. Just write it the same as the complete ionic equation, but without the spectator ions. Ba2+(aq) + SO42-(aq) BaSO4(s) 3. In the equation below, how many electrons does silver lose? 1. 2Ag + 2HCl 2AgCl + H2 *Silver forms a 1+ cation, which means it lost one negatively charged electron. Classify each of the following reactions based on their driving forces: as a. an oxidationreduction reaction, b. acid-base reaction or c. precipitation reaction. (Write the letter a-c). 4. b HNO2 (aq) + KOH(aq) KNO2 (aq) + H2O(l) 5. c K2SO4(aq) + BaCl2(aq) 2KCl(aq) + BaSO4(s) 6. a Mg(s) + I2(g) MgI2(s) Classify each of the following as a. combustion, b. synthesis or c. decomposition. Some may have more than one possible answer. 7. a and b 2Fe(s) + 3O2(g) Fe2O3(s) 8. b Ca + Cl2 CaCl2 9. c H2CO3(g) H2O(g) + CO2(g) Ch. 9 1. Answer the following for this equation: 3NO2(g) + H2O(l) 2 HNO3(aq) + NO(g) If 2.8 mol nitrogen dioxide react with excess water, how much nitric acid will be made? 1.9 mol HNO3 2. You can purify manganese from manganese oxide by reacting it with aluminum. 334 grams manganese (IV) oxide (MnO2) react with 62.2 grams aluminum and make 84.1 grams manganese (Mn) and some aluminum oxide. The balanced equation is: 3MnO2 + 4Al 3Mn + 2Al2O3 a. What is the limiting reactant (reagent)? (Show a calculation that proves which is the limiting reactant). MnO2 = 3.84 mol Al = 2.31 mol To react with 3.84 mol MnO2, 5.12 mol Al is needed. There is not enough Al, so Al = limiting reactant. b. Calculate the theoretical yield of manganese in grams. Use the mol of Al you have (2.31 mol) to calculate the grams of manganese produced. 95.2 g Mn c. Calculate the percent yield of manganese. = actual/theoretical * 100 = 88.3% 10. If you mix NaOH and HCl in the following volumes, which reaction would you expect to have the highest change in temperature? A B C D E Volume Acid (± 0.3 mL) 5 10 15 20 25 Volume of NaOH (± 0.3 mL) 20 20 20 20 20 Ch. 10 11. Define these terms: enthalpy, The law of conservation of energy (1st law of thermodynamics), internal energy, petroleum, fossil fuels, Second Law of Thermodynamics. 12. Give an example of an endothermic reaction. Dissolving some salts in water, such as sodium chloride. 13. Give an example of an exothermic reaction. Combustion of a hydrocarbon. 14. Draw a diagram of an exothermic reaction. Label the a. potential energy of the reactants, b. potential energy of the products and c. the energy released to the surroundings. 15. Draw a diagram of an endothermic reaction. Label the potential energy of the reactants, the potential energy of the products and the energy absorbed from the surroundings. Like the previous question, but draw the energy of the reactants lower than the energy of the products. 16. Are the random motions of molecules faster in hot tea (60 ºC) or a cold can of coke (5 ºC)? The random motions are faster in hot tea. 17. A system does 12 kJ of work and absorbs (= receives) 24 kJ of heat. Calculate the change in internal energy. 12 kJ 18. Convert 4.91 x 10-9 calories to kilojoules. 1 cal = 4.18 J 2.05 x 10-11 kJ 19. Using a candle, 1.43 kj of heat is applied to a 240 gram piece of metal and the specific heat is 0.34 J/g ºC. Calculate the change in temperature in ºC. Q/sm = ∆T = 17.5 ºC 20. For the reaction S + O2 SO2 ∆H = -296 kJ/mol Calculate the change in enthalpy when 22.02 grams of sulfur (S) are burned with excess oxygen. - 203 kJ 21. Given this data: 2S(s) + 3O2(g) 2SO3(g) ∆H = -790.4 kJ 2SO2(g) + O2(g) 2SO3(g) ∆H = -198.2 kJ Calculate ∆H for this reaction: S(s) + O2(g) SO2(g) Show your work. -271.1 kJ 22. Name six uses for fractions of petroleum: (p341) 23. Answer the following for a distillation tower. a. A substance will condense when it reaches a height where the temperature is the same as the boiling point of the substance. b. The hottest part of the tower is at the ( top / bottom ). The coolest part is at the ( top / bottom ). c. Which chemical would condense first, heptane (7 carbons) or decane (10 carbons)? 24. Name one commercial item made from petroleum. What petroleum product is used to make it? Basketballs are made from man-made rubber (from petroleum). Go to http://www.adventuresinenergy.org/Oil-and-Natural-Gas-in-Your-Life/index.html for more ideas. Ch. 20 25. How many valence electrons does a carbon atom have? 4 26. How many covalent bonds can each carbon atom form? 4 27. How is ethanol produced in nature? Yeast makes alcohol by the fermentation of sugar. 28. Be able to write the molecular formula of alkanes, alkenes and alkynes with 1-10 carbon atoms. Example: what is the molecular formula of hexane? C6H14 29. Is hexene saturated or unsaturated? Unsaturated Name molecules containing hydrogen and carbon by the IUPAC system rules. Examples: 30. Name these: a. Hexane b. 2,3-dimethyl hexane H H H H H H H H C C C C C C H H H H H H H H H H C C C H H H H H H H H C C C C H H H C H H H c. 3-methyl-1-butyne d. 4,5-dimethyl-2-hexene CH3 CH CH CH3 CH3 CH CH CH3 e. Methylcyclobutane CH3 g. 3,4-dimethyl-3-phenyl octane CH3 CH2 C CH CH2 CH3 CH3 CH2 CH2 CH3 h. methylcyclohexane Give the IUPAC and common name of substituted benzenes. Example: 31. IUPAC systematic name: 1,2-dimethylbenzene Common name: o-dimethylbenzene CH3 CH3 32. Name organic molecules containing halogens and oxygen. 33. Name these: a. 3-bromo-1-butene b. 2,2-dimethylpentanoic acid CH3 Br CH3 CH3 CH CH CH2 C CH3 O CH2 CH2 C OH c. 2-butanol CH3 d. 2-butanone CH CH2 O CH3 OH e. methyl phenyl ether O C CH2 CH3 CH2 CH2 CH3 CH3 f. Butanal O CH3 CH Be able to draw structural formulas of alkanes, alkenes, alkynes, alcohols, ethers, aldehydes, ketones, carboxylic acids and esters from the name. Examples: 34. 7, 7-diethyl 8,6,6-trimethyl 1-nonene 35. 4-methyl 2-pentyne 36. 2-pentanone 37. Methyl propyl ether 38. ethanal 39. 2-propanol 40. Decanoic acid 41. Propyl methyl ester Be able to identify the functional group (circle it) and identify the molecular class. Example: 42. For the following, circle the functional group and write the class of functional group it is (alcohol, ether, aldehyde, ketone, carboxylic acid or ester). Do NOT write the IUPAC name. a. Class: alcohol b. Class: ester O CH3 CH2 CH2 O-H CH3 C O CH3 43. Be able to draw isomers of an alkane and explain why they are isomers. Example: Draw heptane. Then draw two isomers of it. Explain why they are isomers. Your drawings should have three structural formulas: heptane and two branched molecules with the molecular formula of C7H16. “They are isomers because they have the same number of each type of atom and different structures.” Be able to predict the product of any type of chemical reaction we have learned (a. substitution reaction b. dehydrogenation reaction c. Hydrogenation d. Halogenation) and identify the reaction type. Examples: For the following, name the type of chemical reaction and draw the structural formula of the products. a. substitution reaction b. dehydrogenation reaction c. Hydrogenation d. Halogenation 44. Reaction type: a CH3—CH2—CH3 + Br2 CH3-CH2-CH2Br + HBr 45. Reaction type: d CH2 CH CH2 CH3 + Br2 CH2 CH3 + H2 CH2Br—CHBr—CH2—CH3 46. Reaction type: c CH2 CH CH3—CH2—CH2—CH3 47. Reaction type: b CH3—CH2—CH3 CH2=CH—CH3 Draw the products produced by a condensation reaction between an alcohol and carboxylic acid. Example: 48. Write the structural formula of the ester that is made from propanoic acid and 1octanol. 49. Acrylonitrile can make polymers that are used in paints and clothing fabric, including the fabric used in some of Bly’s clothes. Bly is allergic to wool, so he is happy that he can buy clothes made of acrylic polymer. Draw the dimer formed from two acrylonitrile molecules. + Ch. 21 50. Explain the difference between fibrous and globular proteins. Fibrous proteins give structure to parts of the body. Example: Muscles. Globular proteins are small balls of polypeptides that do different jobs in the body. For example, they send messages. 51. Draw a peptide linkage between glycine and alanine. 52. How does the side chain affect the structure of the protein? (Hint: polarity). When the protein folds, the hydrophilic side groups face outside the protein, while the hydrophobic side groups mostly face inside. 53. Compare the alpha helix and beta pleated sheet. Describe their shapes and how they influence the properties of proteins. The alpha helix forms a spiral (you can draw it if you can’t explain it in words). A pleated sheet makes a zig-zag plane (you can draw it) An alpha helix make stiff structures like your hair. Pleated sheets are strong but flexible. Your muscles are made from proteins that have pleated sheets, for example. 54. Describe how cysteine influences tertiary structure. Cysteine can hold protein folds in place with a disulfide linkage (-S-S-) 55. Explain the difference between primary, secondary and tertiary structure. Primary structure is the order of amino acids, which have hydrophilic and hydrophobic side groups that can influence the structure. The secondary structure is folding over short distances, which can make an alpha helix or a pleated sheet. Tertiary structure is the folding over larger distances.