CHEMISTRY 1A Fall 2010 Final Exam Key YOU MIGHT FIND THE FOLLOWING USEFUL; 0.008314 kj H E ( n)rt R = K mol 0.00418 kj q C cal m w T g C H rxn = H f (products) H f (reactants) Electronegativities H 2.2 Li Be B C N O F 0.98 1.57 2.04 2.55 3.04 3.44 3.98 Na Mg Al Si P S Cl 0.93 1.31 1.61 1.9 2.19 2.58 3.16 K Ca Ga Ge As Se Br 0.82 1.0 1.81 2.01 2.18 2.55 2.96 Rb Sr In Sn Sb Te I Xe 0.82 0.95 1.78 1.96 2.05 2.1 2.66 2.6 Cs Ba Tl Pb Bi Po 0.79 0.89 2.33 2.02 2.0 2.2 1
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. The elements in group 17 on the periodic table are called halogens. 2. 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 is called a(n) hydrogen bond. 3. Isomers are compounds that have the same molecular formula but different molecular structures. 4. The reactant that runs out first and limits the amount of product that can form is called the limiting reactant. 5. A reaction that involves a rapid oxidation accompanied by heat and usually light is called a(n) combustion reaction. 6. The gas in a solution of a gas in a liquid, the solid in a solution of a solid in a liquid, or the minor component in other solutions is called a(n) solute. 7. A(n) strong electrolyte is a substance that ionizes or dissociates completely in an aqueous solution. 8. A(n) strong acid is an acid that donates its H ions to water in a reaction that goes completely to products. Such a compound produces close to one H 3 O ion in solution for each acid molecule dissolved in water. 9. Any chemical change in which at least one element loses electrons, either completely or partially is called oxidation. 10. Potential energy is a retrievable, stored form of energy an object possesses by virtue of its position or state. 11. A(n) exothermic change is a change that leads to heat energy being released from the system to the surroundings. 12. 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. 13. Hydrogenation is a process by which hydrogen is added to an unsaturated triglyceride to convert double bonds to single bonds. This can be done by combining the unsaturated triglyceride with hydrogen gas and a platinum catalyst. 14. A polar molecule or ion (or a portion of a molecule or polyatomic ion) that is attracted to water is called hydrophilic. 15. A(n) catalyst is a substance that speeds a chemical reaction without being permanently altered itself. 2
16. 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. 17. A(n) disulfide bond is a covalent bond between two sulfur atoms of two different amino acids in a protein molecule. 18. A(n) salt bridge is an attraction between a negatively charged side chain and a positively charged side chain in a protein molecule. 19. Hydrolysis is a chemical reaction in which larger molecules are converted into smaller molecules by adding water to their structure. 20. A(n) enzyme is a naturally occurring catalyst. 21. A(n) substrate is a molecule that an enzyme causes to react. 22. A specific section of the protein structure of an enzyme in which the substrate fits and reacts is called a(n) active site. 23. A(n) condensation (or step-growth) polymer is a polymer formed when small molecules, such as water, are released in its formation. This category includes nylon and polyester. 24. A(n) free radical is a molecule with an unpaired electron. 25. The disaccharide sucrose is composed the monosaccharides glucose and fructose. 26. In digestion, proteins are converted into amino acids. 27. Using the skeleton below, draw a Lewis structure for CH 3 CH 2 CONHCH 3. Draw all the resonance structures and the resonance hybrid. Show all formal charges. (6 points each) 3
28. 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 name for each. (8 points) Chemical Formula Type of Substance Name BrF 5 binary covalent bromine pentafluoride Ni(H 2 PO 2 ) 2 ionic with polyatomic ion nickel(ii) dihydrogen phosphite H 2 SO 4 oxyacid sulfuric acid HF(aq) binary acid hydrofluoric acid 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 formula for each. (8 points) Chemical Formula Type of Substance Formula iron(iii) sulfide binary ionic Fe 2 S 3 nitrous acid oxyacid HNO 2 methanol alcohol CH 3 OH sucrose sugar C 12 H 22 O 11 30. 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. (1 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
31. Write the complete equation, the complete ionic equation, and the net ionic equation for the neutralization reaction that takes place between the following reactants. (8 points) Zn(OH) 2 (s) + 2HC 2 H 3 O 2 (aq) Zn(C 2 H 3 O 2 ) 2 (aq) + 2H 2 O(l) Zn(OH) 2 (s) + 2HC 2 H 3 O 2 (aq)zn (aq) + 2C 2 H 3 O 2 (aq) + 2H 2 O(l) Zn(OH) 2 (s) + 2HC 2 H 3 O 2 (aq)zn (aq) + 2C 2 H 3 O 2 (aq) + 2H 2 O(l) 32. Ethanethiol, CH 3 CH 2 SH(g), is a very foul-smelling substance used to odorize natural gas. Write a complete, balanced equation for its combustion. (4 points) CH 3 CH 2 SH(g) + 9/2O 2 (g) 2CO 2 (g) + 3H 2 O(l) + SO 2 (g) Or 2CH 3 CH 2 SH(g) + 9O 2 (g) 4CO 2 (g) + 6H 2 O(l) + 2SO 2 (g) 33. For each of the following, write the type of particle (atoms, molecules, ions, etc.) that form the fundamental structure of the substance, and 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 stronger attractions that hold the particles in the liquid or solid form. (4 points each) a. 2-propanol, CH 3 CH(OH)CH 3 type of particles CH 3 CH(OH)CH 3 molecules type of attraction hydrogen bonds and London forces or butane, CH 3 CH 2 CH 2 CH 3 type of particles CH 3 CH 2 CH 2 CH 3 molecules type of attraction London forces stronger attractions CH 3 CH(OH)CH 3 b. ammonium nitrate, NH 4 NO 3 type of particles NH 4 and NO 3 ions type of attraction ionic bonds or glucose, C 6 H 12 O 6 type of particles C 6 H 12 O 6 molecules type of attraction hydrogen bonds and London forces stronger attractions NH 4 NO 3 c. butanal, CH 3 CH 2 CH 2 CHO type of particles CH 3 CH 2 CH 2 CHO molecules type of attraction dipole-dipole forces and London forces or octanal, CH 3 (CH 2 ) 6 CHO type of particles CH 3 (CH 2 ) 8 CHO molecules type of attraction dipole-dipole forces and London forces stronger attractions CH 3 (CH 2 ) 8 CHO 5
34. 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. (6 points) aldehyde CH 3 CH(CH 3 )CHO 35. 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. (6 points) ether CH 3 CH 2 OCH(CH 3 )CH 3 36. Draw the structure of the tripeptide that forms from linking the amino acids tryptophan, aspartic acid, and asparagine. (4 points) 6
35. 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 -glucose or-glucose? glucose p. Is the linkage shown in this structure an (14) linkage or a (14) linkage? (14) 7
43. Consider the following Lewis Structure for CH 2 CHCHO. (8 points) What is the hybridization for the far left carbon atom? sp 2 What is the hybridization for the far right carbon atom? sp 2 What is the hybridization for the oxygen 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. From left to right: 2 H-C bonds due to 1s-sp 2 overlap 1 C-C bond due to sp 2 -sp 2 overlap 1 C-C bond due to p-p overlap 1 C-C bond due to sp 2 -sp 2 overlap 1 C-O bond due to sp 2 -sp 2 overlap 1 C-O bond due to p-p overlap 1 C-H bond due to sp 2-1s overlap What is the name of the electron group geometry around each carbon atom? trigonal planar Draw a sketch with bond angles. 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. 44. If 21.8 ml of 0.505 M NaOH is required to neutralize 25.00 ml of a phosphoric acid, H 3 PO 4, solution, what is the molarity of the phosphoric acid? (6 points) 3? mol H3PO4 21.8 ml NaOH soln 0.505 mol NaOH 1 mol H3PO4 10 ml = 3 L H3PO 4 soln 25.00 ml H3PO 4 soln 10 ml NaOH soln 3 mol NaOH 1 L = 0.147 M H 3 PO 4 8
45. Acetic acid, CH 3 CO 2 H, 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 CH 3 CO 2 H form from the reaction of 309 kg of CH 3 OH with 543 m 3 of CO(g) at 1 atm and 175 C? (8 points) CH 3 OH + CO CH 3 CO 2 H 1 60.053 kg CH 3CO2H? kg CH3CO2H = 309 kg CH3OH 1 32.042 kg CH3OH = 579 kg CH 3CO 2 H 3 3 10 L K g mol 1 atm? kg CH3CO2H = 543 m CO 3 1 m 0.082058 L g atm 448 K 1 mol CH 3CO2H 60.053 g CH3CO2H 1 kg 3 1 mol CO 1 mol CH3CO2H 10 g = 887 kg CH 3 CO 2 H actual yield 513 kg CH3CO2H % yield = 100 = 100 = 88.6% yield theoretical yield 579 kg CH CO H 3 2 9
Answer the following in short answer form. 41. Explain why lowering the temperature of a gas and why increasing the concentration of a gas by adding gas to a container or decreasing the available volume leads to a greater difference between the pressure calculated from the ideal gas equation and the real or measured pressure. (8 points) 46. Explain why enzyme act on specific substances and form specific products. (6 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. 10