Chemistry 116 Pre-test Some questions from Chem 115 Final exam; Fall 2014

Transcription

1 1. The mass of a sample is 550 milligrams. Which of the following expresses that mass in kilograms? a kg b kg c kg d kg e kg 2. Select the answer that expresses the result of this calculation with the correct number of significant figures and with correct units cm g = cm a g/cm 3 b g/cm 2 c g/cm d g/cm 2 e g/cm 3. What is the mass of one molecule of H3PO4? a g b g c g d g e. Can t be determined- need more information. 4. Consider the isotope 81 Br, Select the combination which lists the correct atomic number, neutron number, and mass number, respectively. a. 35, 46, 81 b. 35, 81, 46 c. 81, 46, 35 d. 46, 81, 35 e. 35, 81, An oxide of nitrogen contains % N. What is the empirical formula of the oxide? a. NO2 b. NO c. N2O3 d. N2O4 e. None of these are correct. 6. How many moles of ClO4 ion are in 354 g of Ca(ClO4)2 (molar mass = )? a mol b mol c mol d mol e mol Page 1 of 6

2 7. Copper is obtained from sulfide ores, such as chalcocite (copper (I) sulfide) by a multistep process. How many moles of oxygen are required to react with 10.0 mol of copper (I) sulfide? a mol b mol c mol d mol e mol Cu2S (s) + O2 (g) Cu2O (s) + SO2 (g) (UNBALANCED) 8. How many liters of M sodium hydroxide are required to neutralize 50.0 ml of M sulfuric acid? NaOH(aq) + H2SO4(aq) Na2SO4(aq) + H2O(l) (UNBALANCED) a L b L c L d L e L 9. Biochemists often study reactions in solutions containing phosphate ions. How many grams of Na2HPO4 (molar mass = ) are in 2.24 L of M Na2HPO4 solution? a. 114 g b g c g d g e. 176 g 10. A fuel mixture used in the early days of rocketry consisted of two liquids, hydrazine (N2H4) and dinitrogen tetroxide (N2O4), which ignite on contact to form nitrogen gas and water vapor. How many grams of nitrogen gas form when g of N2H4 and g of N2O4 are mixed? a. 182 g N2 b g N2 c g N2 d. 131 g N2 e g N2 2 N2H4 + N2O4 3 N2 + 4 H2O (BALANCED) 11. When grams of sand (SiO2) is processed in the reaction below, 51.4 grams of SiC is recovered. What is the percent yield of SiC from this reaction? a % b % c % d % e % SiO2 (s) + 3C (s) SiC (s) + 2CO (g) (BALANCED) Page 2 of 6

3 12. Barium fluoride is used in embalming and in glass manufacturing. Which of the following gives the formula and bonding for barium fluoride? a. BaF2, ionic b. BaF2, covalent c. BaF, ionic d. BaF, covalent e. Ba2F, ionic 13. In the following balanced redox reaction, the oxidizing agent is, and the reactant that is oxidized is. 3 Cl2(g) + 2 Cr(OH)3(s) + 10 OH (aq) 6 Cl (aq) + 2 CrO4 2 (aq) + 8 H2O a. CrO4 2-, Cl b. Cl2, Cr(OH)3 c. Cr(OH)3, OH d. Cl, Cl2 e. Cr(OH)3, Cl2 14. Aqueous solutions of calcium chloride and sodium sulfate react to form calcium sulfate and sodium chloride. Write the net ionic equation for this reaction. The SPECTATOR ions are: a. Ca 2+ (aq) and SO4 2 (aq) b. Ca 2+ (aq), SO4 2 (aq), and CaSO4 (s) c. Na + (aq) and Cl (aq) d. All are spectator ions. e. There are no spectator ions in this reaction. 15. Which of the following substances is considered a strong electrolyte when dissolved in water: a. CH3OH (methyl alcohol) b. NH4Cl c. NH3 d. HC2H3O2 (acetic acid) e. None of the above, since all are weak electrolytes. 16. Given the standard heat of formation, H f, values below; what is the standard enthalpy change for the following reaction. TiCl4 (l) + 2 H2O(l) TiO2 (s) + 4 HCl(g) H =? Substance H2O(l) H2O(g) TiCl4 (l) HCl(g) TiO2(s) H f (kj/mol) a kj b kj c kj d kj e kj Page 3 of 6

4 17. If 100. J of heat was added to each of the following, which would have the lowest final temperature? a. 1 g Zn at 20. C (CP = 0.40 J/g C) b. 1 g Cu at 20. C (CP = J/g C) c. 1 g H2O at 20. C (CP = 4.18 J/g C) d. 1 g Al at 20. C (CP = 0.89 J/g C) e. All would end up at the same final temperature. 18. Calculate the heat involved when 1.80 g of octane, C8H18, is reacted. a kj b kj c kj d. 224 kj e kj C8H /2 O2 8 CO2 + 9 H2O H = 5490 kj 19. Ethyl chloride, C2H5Cl, has heat of vaporization is 26.4 kj/mol. Calculate the amount of heat removed by vaporization of 10.0 g of ethyl chloride. a kj b kj c. 171 kj d. 264 kj e kj 20. The specific heat of copper is J/g C. A block of copper initially at 22.5 C absorbs 3.82 kj of heat and warms to a final temperature of 53.0 C. What is the mass of the copper block? a g b g c. 187 g d. 325 g e. 441 g 21. A 13.0 gram piece of metal at 80.0 C was added to 50.0 grams of H2O at 20.0 C. The final temperature of the resulting mixture was 23.1 C. The specific heat of the metal is: a J/g C b J/g C c J/g C d J/g C e. 3.1 J/g C 22. A(n) chemical reaction releases heat to the surroundings and has a value of H. a. spontaneous, positive b. endothermic, negative c. exothermic, negative d. endothermic, positive e. exothermic, positive Page 4 of 6

5 23. Calculate H 0 of the reaction P4 (s) + 10 Cl2 (g) 4 PCl5 (s) H 0 =? given the following thermochemical information: a. 444 kj b kj c kj d kj e kj PCl3 (l) + Cl2 (g) PCl5 (s) H = 124 kj 4 PCl3 (l) P4 (s) + 6 Cl2 (g) H = kj 24. Which element has the lowest first ionization energy? a. F b. Cl c. Br d. I e. Te 25. Which element has the largest atomic radius? a. Al b. Si c. P d. S e. Cl 26. How many bonding electrons are there in the Lewis structure of CN? a. 1 b. 2 c. 4 d. 6 e Which one of the following does not contain a polar covalent bond? a. ICl b. I2 c. CO d. HF e. NO 28. The shape of CO3 2 ion is. a. Bent b. Tetrahedral c. Pyramidal d. T-shaped e. Trigonal planar Page 5 of 6

6 29. Arrange the following in order of increasing boiling point. CH3CH2OH CH3CH2CH3 H 3 C-O-CH3 CH3CH2NH2 I II III IV a. All have the same boiling point b. IV < III < II < I c. II < III < IV < I d. I < IV < III < II e. II < III < I < IV 30. What phase transition occurs as one moves from point A to point B in the following phase diagram? a. Liquid to gas (evaporation) b. Gas to liquid (condensation) c. Solid to gas (sublimation) d. Solid to liquid (melting/fusion) e. Liquid to solid (freezing) 31. A 459 ml gas sample at 245 C and 855 torr would occupy what volume at STP? a. 981 ml b. 575 ml c. 463 ml d. 272 ml e. 215 ml 32. A gas sample occupies a volume of 18.9 liters at 35.6 C and 735 torr. How many moles of gas are there in the sample? a mole b mole c mole d mole e mole 33. The density of CO2 (g) at 25 C and 715 torr is: a g/l b g/l c g/l d g/l e g/l key 1. C 2. C 3. D 4. A 5. A 6. E 7. B 8. C 9. E 10. D 11. C 12. A 13. B 14. C 15. B 16. D 17. C 18. E 19. B 20. D 21. A 22. C 23. B 24. E 25. A 26. D 27. B 28. E 29. C 30. D 31. D 32. A 33. B Page 6 of 6