CHEM 171 EXAMINATION 1 October 9, 008 Dr. Kimberly M. Broekemeier NAME: Key I A II A III B IV B V B VI B VII B VIII I B II B III A IV A V A VI A VII A inert gase s 1 H 1.008 Li.941 11 Na.98 19 K 9.10 7 Rb 85.4 55 Cs 1.9 87 Fr () 4 Be 9.01 1 Mg 4.1 0 Ca 40.08 8 Sr 87. 5 Ba 17. 88 Ra.0 1 Sc 44.9 9 Y 88.91 57 * La 18.9 89 * Ac (7) Ti 47.90 40 Zr 91. 7 Hf 178.4 104 Rf (1) V 50.94 41 Nb 9.91 7 Ta 180.9 105 Db () 4 Cr 5.00 4 Mo 95.94 74 W 18.8 10 Sg () 5 Mn 54.94 4 Tc 98.91 75 Re 18. 107 Bh () Fe 55.85 44 Ru 101.0 7 Os 190. 108 Hs (5) 7 Co 58.9 45 Rh 10.9 77 Ir 19. 109 Mt () 8 Ni 58.71 4 Pd 10.4 78 Pt 195.0 110 (9) 9 Cu.55 47 Ag 107.8 79 Au 19.9 111 (7) 0 Zn 5.7 48 Cd 11.4 80 Hg 00.5 11 (77) 5 B 10.81 1 Al.98 1 Ga 9.7 49 In 114.8 81 Tl 04. 11? C 1.01 14 Si 8.09 Ge 7.59 50 Sn 118. 8 Pb 07. 114 (89) 7 N 14.01 15 P 0.97 As 74.9 51 Sb 11.8 8 Bi 08.9 8 O 1.00 1 S.0 4 Se 78.9 5 Te 17. 84 Po (10) 9 F 19.00 17 Cl 5.45 5 Br 79.90 5 I 1.9 85 At (10) He 4.00 10 Ne 0.17 18 Ar 9.95 Kr 8.80 54 Xe 11. 8 Rn () 58 Ce 140.1 90 Th.0 59 Pr 140.9 91 Pa (1) 0 Nd 144. 9 U 8.0 1 Pm (147) 9 Np (7) Sm 150.4 94 Pu (4) Eu 151.9 95 Am (4) 4 Gd 157. 9 Cm (47) 5 Tb 158.9 97 Bk (47) Dy 1.5 98 Cf (51) 7 Ho 14.9 99 Es (54) 8 Er 17. 100 Fm (5) 9 Tm 18.9 101 Md (5) 70 Yb 17.0 10 No (54) 71 Lu 174.9 10 Lw (57) I. Short Answer (4 points total)
1) Give the missing name, symbol or formula for each of the following: ammonium sulfide _(NH 4 ) S hydrogen carbonate ion _HCO - diiodine heptoxide I O 7 cobalt(iii) nitrate Co(NO ) Ca(ClO 4 ) calcium perchlorate AsF arsenic trifluoride Rh O rhodium (III) oxide HIO (aq) iodic acid ) Balance the following reaction scheme with whole number coefficients: 4 NH (g) + _5 O (g) 4 NO(g) + H O(l) ) Write the corresponding value (to sig figs) for each of the following unit conversions..4 g/cm =.4 mg/mm 1.0 μm = 1.0 x 10 pm g 10 mg 100 cm m.4 x x ( ) x ( ) =.4 cm g m 1000 mm 1 m 10 pm 10 m m 1.0 m x x = 1.0 x 10 4) The species 5 Cu + has 9 protons, neutrons, and 7 electrons. 5) What is the average mass of an oxygen atom in amu? 1.00 amu What is the mass of a mole of naturally occurring oxygen atoms in g? 1.00 g ) Consider the elements of the third period. Identify, by symbol, ONE element which has the listed characteristic. If none of the elements in the period has this property, answer NONE. is a non-metal _Si, P, S, Cl, Ar is an alkali metal Na is a halogen Cl forms only + ions Mg forms an anion with a - charge S exists as diatomic molecules in its elemental state Cl 7) Identify each of the following as a chemical process (C) or a physical process (P). loss of electrons C dissolving NaCl into water P 8) Identify the following as an intensive (I) or extensive (E) property. mass E density I 9) What is the molar mass (with units) for Cu (PO 4 )? 80.59 g/mol 10) What is the charge on the copper ion in the compound given in question 9? +
II. Multiple Choice ( points total) Circle the letter corresponding to the single BEST answer for each question. 1) In SI, the prefix used to indicate 10-1 has which symbol and name? a. n and nano c. p and pico e. m and milli b. f and femto d. c and centi f. μ and micro ) Which of the following is not a basic or fundamental SI unit? a. liter c. Kelvin e. kilogram b. meter d. Ampere f. mole ) Which one of the following species has the greatest mass? a. a mol of hydrogen molecules c. a hydrogen molecule e. a neutron b. a mol of hydrogen atoms d. a hydrogen atom f. a proton 4) Which one of the following represents the compounds which are ionic? i. As 4 S ii. NaCl iii. PCl iv. BaSO 4 v. NH 4 NO vi. Cl O a. i, vi c. i, iii, vi e. ii, iii, iv, v b. ii, iv, v d. iii, v f. all are ionic 5) Which one of the following has the greatest mass percent sodium? a. NaCl c. Na (PO 4 ) e. Na O b. Na S d. NaBr f. Na (AsO 4 ) ) What is the mass, in g, of 0.15 mol of calcium fluoride? a. 4.90 g c. 9.7 g e..8 g b. 5.01 g d. 1.5 g f. 7.9 g 7) Which of the following, in water, would be strong electrolytes? i) HNO ii) NaOH iii) HCH COO iv) H SO 4 v) H PO 4 vi) NH a. i, iv c. ii, vi e. vi b. i, iii, iv, v d. i, ii, iv f. ii, iv
8) A compound containing only nitrogen and oxygen is known to be 5.9 % N by mass. What is the empirical formula of this compound? a. N O 5 c. NO e. N O 4 b. NO d. NO 5 f. N O 9) How many mol of sodium are in 5 g of Na CO? (molar mass = 10.0 g/mol) a. 4.5 mol c. 0.471 mol e..1 mol b. 0.94 mol d. 1.7 mol f..7 mol 10) The equation below describes the reaction between elemental sodium and elemental chlorine. If 1.00 mol Na(s) is reacted with.00 mol Cl (g), and the reaction goes to completion, which is the limiting reactant, and how many moles of product are formed? Na(s) + Cl (g) NaCl(s) a. sodium and 1.00 mol NaCl b. chlorine and 1.00 mol NaCl c. stoichiometric amounts and 1.00 mol NaCl d. sodium and.00 mol NaCl e. chlorine and.00 mol NaCl f. stoichiometric amounts and.00 mol NaCl 11) Last week in lab, the masses and volumes of solutions were measured in order to determine the density (mass/vol) of a solution of unknown density. In one part, the acccumulated mass of a beaker and its contents was plotted versus the volume of the solution added to the beaker from a buret. One set of data yielded the curve fit equation: y = 1.059 x + 1.8. What was the mass of the breaker and contents after addition of 5.00 ml of the unknown solution to the beaker? a. 100. b. 144.7 c. 101.8 d. 15. e. 151.8 f. 17.9 1) From your observations in the lab (Identification of Unknown Solutions), which one of the following solutions forms an odor when treated with sulfuric acid? a. Ba(OH) (aq) c. K SO 4 (aq) e. NH (aq) b. NH 4 Cl(aq) d. HCl(aq) f. NaC H O (aq) III. Problems (18 points total) For each of the problems on the following page, show all setup, logic and work. Place units on all quantities, use three significant figures, and place final result in the space provided (include units!!)
1) A particular organic compound contains only carbon, hydrogen and sulfur. A.57 g sample of the compound is processed in a combustion analyzer, which resulted in the production of.5 g CO, 1.9 g H O, and.4 g SO. What is the empirical formula for this compound? Molar mass: H O (18.01 g/mol) CO (44.01 g/mol) SO (4.07 g/mol) Compound + O CO + H O + SO mol CO 1 C.5 g CO x x = 0.54 mol C 44 g mol CO Emp. Form. = CH 4 S mol H O mol H 1.9 g H O x x = 0.14 mol H 18.01 g mol H O mol SO 1 mol S.4 g SO x x = 0.054 4.0 g mol SO Divide by smallest number of moles (0.54) to get a ratio of 1C:4H:1S ) A hypothetical element (E) has an average atomic mass of 5.85 u. In nature, it exists as two isotopes: 5 E (exact mass = 4.789 u) and 7 E (exact mass =.785 u). Determine the percent abundance of each isotope. % 5 E 75.15 % 5.85 = (x)(4.789) + (1-x)(.785) % 7 E 4.85 % Solve for x: 5.85 = 4.789x +.785.785x -1.500 = -1.99 x x = 0.7515 ) The following reaction describes the production of elemental iodine in small quantities from readily available potassium iodide. When 4.50 g of KI(s) is treated with.9 g elemental chlorine,.5 g of elemental iodine is recovered: Cl (g) + KI(s) KCl(s) + I (s) a. Which reactant is the limiting reagent? (Prove by calculation) KI mol KI 1 mol I 4.5 g KI x x = 0.01 mol I 1.0 g mol KI mol Cl 1 mol I.9 g Cl x x = 0.079 mol I 70.90 g 1 mol Cl The limiting reagent is KI, since less I can be formed. The same type of calculation could have been done with determing the amount of KCl formed. Convert moles to mass: 0.01 mol I x 5.8 g/mol =.45 g theoretical yield. Actual yield/theoretical yield x 100 = percentage yield.5/.45 x 100 = 94. b. What is the percentage yield of elemental iodine? 94.%