CHEMISTRY 1A Spring 2010 Final Exam Key

Transcription

1 CHEMISTRY 1A Spring 2010 Final Exam Key YOU MIGHT FIND THE FOLLOWING USEFUL; kj ΔH = ΔE + (Δn)RT R = K mol kj q = C cal + mw T K mol H rxn = Σ H f (products) Σ H f (reactants) Electronegativities H 2.2 Li Be B C N O F Na Mg Al Si P S Cl K Ca Ga Ge As Se Br Rb Sr In Sn Sb Te I Xe Cs Ba Tl Pb Bi Po

2 Answer the following by writing the word, words, letter, letters or number in each blank that best completes each sentence. (1 point each blank) 1. A(n) heterogeneous mixture is a mixture with two or more phases. 2. Malleable means capable of being extended or shaped by the blows of a hammer. 3. The name of group 2 on the periodic table is alkaline earth metals. 4. Isotopes are atoms that have the same number of protons but different numbers of neutrons. They have the same atomic number but different mass numbers. 5. Valence electrons are the electrons that are most important in the formation of chemical bonds. The number of valence electrons for the atoms of an element is equal to the element s A-group number on the periodic table. 6. Hydrocarbons are compounds that contain only carbon and hydrogen. 7. Isomers are compounds that have the same molecular formula but different molecular structures. 8. A(n) hydrogen bond is the intermolecular attraction between a nitrogen, oxygen, or fluorine atom of one molecule and a hydrogen atom bonded to a nitrogen, oxygen, or fluorine atom in another molecule. 9. A(n) strong electrolyte is a substance that ionizes or dissociates completely in an aqueous solution. 10. A(n) weak acid is a substance that is incompletely ionized in water due to the reversibility of the reaction that forms hydronium ions, H 3O +, in water. They yield significantly less than one H 3O + ion in solution for each acid molecule dissolved in water. 11. Oxidation is any chemical change in which at least one element loses electrons, either completely or partially. 12. Potential energy is a retrievable, stored form of energy an object possesses by virtue of its position or state. 13. A(n) exothermic change is a change that leads to heat energy being released from the system to the surroundings. 14. Specific heat capacity is the heat necessary to increase the temperature of one gram of pure substance by one kelvin (or one degree Celsius). 15. A(n) excited state is the condition of an atom that has at least one of its electrons in orbitals that do not represent the lowest possible potential energy. 16. Paramagnetic means having a net magnetic field due to having at least one unpaired electron. 17. A(n) cis isomer is a structure that has like groups on different carbons (which are linked by a double bond) and on the same side of the double bond. 2

3 18. A polar molecule or ion (or a portion of a molecule or polyatomic ion) that is attracted to water is called hydrophilic. 19. A(n) catalyst is a substance that speeds a chemical reaction without being permanently altered itself. 20. A(n) peptide bond is an amide functional group that forms when the carboxylic acid group on one amino acid reacts with the amine group of another amino acid. 21. A(n) substrate is molecule that an enzyme causes to react. 22. A(n) active site is a specific section of the protein structure of an enzyme in which the substrate fits and reacts. 23. A(n) condensation reaction is a chemical reaction in which one of the products is a small molecule, such as water. 24. Hydrolysis is a chemical reaction in which larger molecules are converted into smaller molecules by adding water to their structure. 25. Lactose (milk sugar) is a disaccharide composed of the two monosaccharides glucose and galactose. 26. The digestion products of triglycerides are glycerol and fatty acids. 27. Draw Lewis structures for each of the following, a. Nitrous acid, HNO 2 (3 points) b. Cis and trans isomers of 2-butene, CH 3CHCHCH 3 (4 points) 28. Draw all the resonance structures and the resonance hybrid for hydrogen carbonate, HCO 3. Use the following skeleton. Include formal charges. (5 points) 3

4 29. Identify each of the following as a binary covalent compound, a binary ionic compound, a binary acid, an ionic compound with a polyatomic ion, an oxyacid, an alcohol, or a sugar. Write the name for each. (7.5 points) Chemical formula Type of substance Name H 2SO 3 oxyacid sulfurous acid Cl 2F 8 binary covalent dichlorine octafluoride HF(aq) binary acid hydrofluoric acid Fe(HSO 4) 2 ionic with polyatomic ion Iron(II) hydrogen sulfate Al 2(HPO 4) 3 ionic with polyatomic ion aluminum hydrogen phosphate 30. Identify each of the following as a binary covalent compound, a binary ionic compound, a binary acid, an ionic compound with a polyatomic ion, an oxyacid, an alcohol, or a sugar. Write the formula for each. (7.5 points) Chemical name Type of substance Formula 2-propanol alcohol CH 3CHOHCH 3 potassium hypochlorite ionic with polyatomic ion KClO hydrogen chloride binary covalent HCl hypophosphorous acid oxyacid H 3PO 2 potassium dihydrogen phosphate ionic with a polyatomic ion KH 2PO Identify each of the following as (1) a strong, weak, or nonelectrolyte and (2) a strong acid, weak acid, strong base, weak base, or neutral. (3/4 point each box) Substance Strong, weak, or nonelectrolyte Strong acid, weak acid, strong base, weak base, or neutral ammonia Weak electrolyte Weak base HNO 3(aq) Strong electrolyte Strong acid phosphoric acid Weak electrolyte Weak acid NaNO 2 Strong electrolyte Weak base sodium hydrogen sulfate Strong electrolyte Weak acid 4

5 32. Write the complete equation, the complete ionic equation, and the net ionic equation for the neutralization reaction that takes place between the following reactants. (6 points) Cu(OH) 2(s) + 2HC 2H 3O 2(aq) Cu(C 2H 3O 2) 2(aq) + 2H 2O(l) Cu(OH) 2(s) + 2HC 2H 3O 2(aq) Cu 2+ (aq) + 2C 2H 3O 2 (aq) + 2H 2O(l) Cu(OH) 2(s) + 2HC 2H 3O 2(aq) Cu 2+ (aq) + 2C 2H 3O 2 (aq) + 2H 2O(l) 33. Draw the Lewis structure and condensed formula for the line drawing below. Classify it as an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide. (5 points) ether CH 3CH 2OCH(CH 3)CH Draw the line drawing and condensed formula for the Lewis structure below. Classify it as an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide. (5 points) CH 3C(CH 3)CH 2CH 2CHO aldehyde 5

6 35. For each of the following, write the name of the type of attraction holding these particles in the solid and liquid form. Indicate the formula in each pair that represents the substance that you would expect to have the higher melting point and boiling point. (3 points each) a. sodium nitrate, NaNO 3 type of attraction ionic bonds or methylamine, CH 3NH 2 type of attraction hydrogen bonds and London forces higher m.p. and b.p. NaNO 3 b. Decanoic acid, CH 3(CH 2) 8CO 2H type of attraction hydrogen bonds and London forces or formic acid, HCO 2H type of attraction hydrogen bonds and London forces higher m.p. and b.p. CH 3(CH 2) 8CO 2H c. diamond, C(dia) type of attraction covalent bonds or acetone, CH 3COCH 3 type of attraction dipole-dipole attractions and London forces higher m.p. and b.p. diamond 36. Identify each of the following triglycerides as saturated or unsaturated. Which is more likely to be a solid at room temperature, and which is more likely to be a liquid? (4 points) saturated solid unsaturated liquid 6

7 37. Draw the structure of the tripeptide that forms from linking the amino acids tryptophan, aspartic acid, and asparagine. (4 points) 38. Explain why each enzyme only acts on a specific molecule of a specific type of reaction. (5 points) The active site of each enzyme has a physical shape that only allows certain substrates to fit into it. Binding groups attract specific substrates to the active site, which is the portion of the enzyme where the reaction occurs. The orientation of these groups fit certain groups on certain substrates so that the substrates are placed in the correct orientation to react. Catalytic groups stabilize the intermediates and therefore speed reactions. The orientation of these groups also fit certain groups on certain substrates. 7

8 39. Consider the following Lewis structure for ethamide, CH 3CONH 2. (12 points) What is the hybridization for left carbon atoms? sp 3 What is the hybridization for middle carbon atoms? sp 2 What is the hybridization for the oxygen atom? sp 2 What is the hybridization for the nitrogen atom? sp 2 Write a description of the bonding, stating whether each bond is sigma, pi, or part of a delocalized pi system and by stating which atomic orbitals overlap to form the bonds. 3 σ H-C bonds due to 1s-sp 3 overlap 1 σ C-C bonds due to sp 3 -sp 2 overlap 1 σ C-O bonds due to sp 2 -sp 2 overlap 1 σ C-N bonds due to sp 2 -sp 2 overlap 1 delocalized pi system due to p orbitals on O, C, and N overlapping in parallel What is the name of the electron group geometry around the left carbon atom? tetrahedral What is the name of the electron group geometry around the middle carbon atom? trigonal planar What is the name of the electron group geometry around the nitrogen atom? trigonal planar Draw a sketch with bond angles. 8

9 40. Identify each of the following structures as representing a carbohydrate, amino acid, protein (and peptide), triglyceride, or steroid. (1½ points each) a. amino acid b. carbohydrate c. triglyceride b. peptide 9

10 41. Look at the front screen in the lecture hall and answer the following questions. (1 point each) a. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? alcohol b. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? aldehyde c. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? carboxylic acid d. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? ether e. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? ester f. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? alkyne g. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? amine h. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? amide i. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a protein), a protein, or a steroid? peptide j. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a protein), a protein, or a steroid? amino acid k. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a protein), a protein, or a steroid? steroid l. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a protein), a protein, or a steroid? triglyceride m. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a protein), a protein, or a steroid? protein n. Does this image represent glucose or fructose? fructose o. Does this image represent α-glucose or β-glucose? α glucose p. Is the linkage shown in this structure an α(1 4) linkage or a β(1 4) linkage? β(1 4) 10

11 42. Identify each of the following as representing nylon, polyester, polyethylene, poly(vinyl chloride), polypropylene, or polystyrene. (In each case, the n represents some large integer.) (6 points) a. polyethylene b. polyester c. polypropylene d. polystyrene e. nylon f. poly(vinyl chloride) 11

12 For the following calculations, be sure to show your work and round your final answer off correctly. NOTE: Remember that there is part credit for each problem. Even if you cannot do all of a problem, be sure to set up as much of it as you can. 43. If 12.0 ml of 1.34 M NaOH is required to neutralize ml of a sulfuric acid, H 2SO 4, solution, what is the molarity of the sulfuric acid? (5 points) 3? mol H 2SO ml NaOH soln 1.34 mol NaOH 1 mol H2SO4 10 ml = 3 L H2SO 4 soln ml H2SO 4 soln 10 ml NaOH soln 2 mol NaOH 1 L = M H 2SO Acetic acid, CH3CO2H, can be made from methanol and carbon monoxide in the following reaction, which uses a rhodium/iodine catalyst. What is the percent yield when 513 kg of liquid CH3CO2H form from the reaction of 309 kg of CH3OH with 543 m3 of CO(g) at 1 atm and 175 C? (6 points) CH 3OH + CO CH 3CO 2H 1 x kg CH 3CO2H? kg CH3CO2H = 309 kg CH3OH = 579 kg CH3CO2H 1 x kg CH3OH L K mol 1 atm? kg CH3CO2H = 543 m CO 3 1 m L atm 448 K 1 mol CH 3CO2H g CH3CO2H 1 kg 3 1 mol CO 1 mol CH3CO2H 10 g = 887 kg CH 3CO 2H actual yield 513 kg CH3CO2H % yield = 100 = x 100 = 88.6% yield theoretical yield 579 kg CH CO H