CHM1045 Exam 2 Chapters 3, 4, & 10

Transcription

1 1. Upon analysis, a compound is found to contain 22.8% sodium, 21.8% boron, and 55.4% oxygen. What is its empirical formula? a. NaBO b. NaB 2 O 5 c. Na 2 B 4 O 7 d. Na 3 BO 4 e. None of the above. 2. The number of reactant atoms must be equal to the number of product atoms in a balanced chemical equation. a. True b. False 3. Avogadro's number equals the number of a. Atoms in one mole of Al b. Molecules in one mole of O 2 c. Formula units in one mole of NaCl d. Marbles in one mole of marbles e. All of the above CHM1045 Exam 2 Chapters 3, 4, & A g sample of an unknown ionic compound containing bromine is dissolved in water and the solution is treated with enough silver nitrate to precipitate all the bromide ion. If 18.79g of silver bromide is recovered, which of the following compounds could be the unknown? a. Aluminum bromide b. Calcium bromide c. Magnesium bromide d. Potassium bromide e. Sodium bromide 5. The van der Waals equation must be used instead of the ideal gas law at a. extremely high temperatures b. extremely high volumes c. extremely high pressures d. if there is more than one type of gas molecule present e. more than one above 6. Which compound has the atom with the most positive oxidation number? a. NO b. N 2 O c. O 2 - d. IO 4 e. 2- SO 4 f. P 2 O 5

2 7. At standard temperature and pressure conditions (STP), one mole of each of the halogens will occupy L. a. True b. False 8. What is the coefficient of H 2 O when the following equation is properly balanced with smallest set of whole numbers? Al 4 C 3 + H 2 O Al(OH) 3 + CH 4 a. 3 b. 4 c. 6 d. 12 e Water can act as a? a. Solvent b. Solute c. Both d. neither 10. You have a large sealed flask that contains both hydrogen and radon gas molecules. Which statement is true: a. The hydrogen molecules have a larger average kinetic energy b. The radon molecules have a larger average kinetic energy c. The hydrogen molecules have a larger root-mean-square speed d. The radon molecules have a larger root-mean-square speed e. More than one statement above is true. 11. Which of the following is oxidized in the reaction: Fe + Ag 2 O FeO+ 2Ag a. Ag b. Ag2O c. Fe d. FeO e. More than one of the above choices is correct. 12. Which substance is the least soluble in H 2 O? a. K 2 CO 3 b. KHCO 3 c. Ca(HCO 3 ) 2 d. CaCO 3

3 13. How many H atoms are in 3.4 g of C 12 H 22 O 11? Molar mass C 12 H 22 O g mol -1. a b c d How many ml of 8.00 M HCl are needed to prepare 150. ml of a 1.60 M HCl solution? Molar mass HCl g mol -1. a ml b ml c ml d ml 15. The reaction of ethanol, C 2 H 5 OH, with oxygen is a popular classroom demonstration. Balance the equation to find the number of moles of gaseous products formed per mole of ethanol. a. 2 b. 3 c. 4 d. 5 C 2 H 5 OH(g) + O 2 (g) CO 2 (g) + H 2 O(g) 16. Ethanol burns in excess oxygen to form CO 2 (g) and H 2 O(g) (see previous question). What value is closest to the volume of CO 2 (g), measured at 200K and 1 atm, produced from the combustion of 0.25 mol of C 2 H 5 OH(g)? a. 5 L b. 8 L c. 10 L d. 15 L 17. Ammonia is produced from the reaction of nitrogen gas with hydrogen gas. In a particular experiment, 0.25 mol of ammonia is formed when 0.5 mol of nitrogen gas is reacted with 0.5 mol of hydrogen gas. What is the percent yield? a. 75% b. 50% c. 33% d. 25%

4 18. Under which conditions will a gas behave most ideally? a. low P and high T b. low P and low T c. high P and low T d. high P and high T 19. The mass of 560 cm 3 of a gas at 0 C and 1 atm is 1.60 g. Which gas is it? a. O 2 b. CO 2 c. SO 2 d. Cl Which equation represents an oxidation-reduction reaction? a. H 2 SO 4 + 2NH 3 (NH 4 ) 2 SO 4 b. H 2 SO 4 + Na 2 CO 3 Na 2 SO 4 + H 2 O + CO 2 c. 2K 2 CrO 4 + H 2 SO 4 K 2 Cr 2 O 7 + K 2 SO 4 + H 2 O d. 2H 2 SO 4 + Cu CuSO 4 + 2H 2 O + SO Which are strong acids? I. HI II. HNO 3 III. H 2 SO 3 a. II only b. I and II only c. II and III only d. I, II and III 22. What products result when aqueous solutions of CuCl 2 and (NH 4 ) 2 S are mixed? a. CuS(aq) and NH 4 Cl(s) b. CuS(s) and NH 4 Cl(aq) c. CuS(aq) and NH 4 Cl(g) d. CuS(s) and NH 4 Cl(s) 23. A chloride salt of rhenium contains 63.6% Re by mass. What is its empirical formula? a. ReCl b. ReCl 2 c. ReCl 3 d. ReCl The amount of chloride ion in a water sample is to be determined by adding excess silver nitrate. If 1.0 g of silver chloride is precipitated, what mass of chloride ion is in the original sample? Molar Mass: AgNO g mol 1 ; AgCl g mol 1 a g b g c g d g

5 25. How many millimoles of methane, CH 4, are present in 6.4 g of this gas? Molar mass CH g mol 1. a b. 4.0 c. 40. d. 4.0 x A 1.50 ml sample of a sulfuric acid solution from an automobile storage battery is titrated with 1.47 M sodium hydroxide solution to a phenolphthalein endpoint, requiring ml. What is the molarity of the sulfuric acid solution? a M b M c M d M 27. According to the equation SnO 2 + 2H 2 Sn + 2H 2 OWhat volume of hydrogen, measured at 1 atm and 273 K, is required to react with 2.00 g of SnO 2? Molar mass SnO g mol 1. a L b L c L d L 28. Three balloons are filled with the same number of atoms of He, Ar, and Xe, respectively. Which statement is true under the same conditions of temperature and pressure? a. The balloons contain the same mass of gas. b. All balloons have the same volume. c. The densities of the three gases are the same. d. The average speed of the different types of atoms is the same. 29. A heterogeneous system is produced when moles of solid NaCl is added to 0.10 L of 0.10 M Pb(NO 3 ) 2. Which ion is present in the aqueous phase at the highest concentration? a. Cl b. NO 3 c. Pb 2+ d. Na Which expression gives the fraction by mass of nitrogen in ammonium dihydrogen phosphate? a. 14 / 115 b. 28 / 115 c. 28 / 132 d. 14 / Adipic acid,hooc(ch 2 ) 4 COOH, is used in making nylon. What is the total number of atoms in 1.0 g of adipic acid? Molar Mass, g mol 1 adipic acid a. 20 b. 4.1 x c. 8.2 x d. 7.2 x 10 24

6 32. A sample of neon gas has a volume of 248 ml at 30. C and a certain pressure. What volume would it occupy if it were heated to 60. C at the same pressure? a. 226 ml b. 273 ml c. 278 ml d. 496 ml 33. A gas is collected in the flask shown here. What is the pressure exerted by the gas if the atmospheric pressure is 735 mmhg? a. 42 mmhg b. 693 mmhg c. 735 mmhg d. 777 mmhg 34. Helium is often found with methane, CH 4 How do the diffusion rates of helium and methane compare at the same temperature? Helium diffuses a. sixteen times as fast as methane. b. four times as fast as methane. c. twice as fast as methane. d. at the same rate as methane. 35. Nickel metal is added to a solution containing 1.0 M Pb 2+ (aq) and 1.0 M Cd 2+ (aq). Which reaction(s) will occur? Reaction 1: Ni(s) + Pb 2+ (aq) Pb(s) + Ni 2+ (aq) Reaction 2: Ni(s) + Cd 2+ (aq) Cd(s) + Ni 2+ (aq) a. 1 only b. 2 only c. both 1 and 2 d. neither 1 nor 2