Past Exam for Principles of Chemistry I with Cheat Sheet | CHEM 1251, Exams of Chemistry

Download Past Exam for Principles of Chemistry I with Cheat Sheet | CHEM 1251 and more Exams Chemistry in PDF only on Docsity! Page Points Score Grader 1 26 2 22 3 27 4 25 Total 100 Chemistry 1251 Exam #2 (75 minutes) March 26, 2009 Last Name First Name Signature SID# 800- Please read each question carefully and answer it completely and clearly. Most of the factual information you need is contained in the text of the problem. Answer the questions you find easy first; questions which appear difficult at first usually require objective rethinking to abandon incorrect assumptions. Always keep in mind the intended examination topics if a problem appears too hard. The quiz should have 6 pages. Individual point values are given in the corner of each answer space. Only answers in the provided boxes will be graded. You must show your work to receive any credit for problems involving calculations. All calculated answers must include units, and should be rounded to the appropriate number of significant figures! 88.91 Useful Constants Avogadro’s Number (N) 6.022 x 1023 /mol Mass of electron 9.11 x 10-31 kg Specific heat of H2O (l) 4.184 J/(g · ºC) Mass of neutron 1.675 x 10-27 kg Planck’s constant (h) 6.63 x 10-34 J · s Mass of proton 1.673 x 10-27 kg Speed of light in a vacuum (c) 3.00 x 108 m/s Electron charge 1.602 x 10-19 C Conversion Factors 1 cm3 = 1 mL giga (G) = 109 1 Hz = 1 s-1 mega (M) = 106 TºC = (TºF – 32 °F) x (5°C)/(9°F) kilo (k) = 103 TK = TºC + 273.15 deci (d) = 10-1 1 amu = 1.66 x 10-24 g centi (c) = 10-2 1 cal = 4.184 J milli (m) = 10-3 1 J = 1 N · m micro (μ) = 10-6 1 N = 1 kg · m s2 nano (n) = 10 -9 1 J = 1 kg · m2 s2 pico (p) = 10 -12 1 Angstrom (Å) = 10-10 m femto (f) = 10-15 Formulae d = mV % yield = actual yield theoretical yield x 100 % Molarity (M) = moles of solute volume of solution E = κ Q1 Q2 d c = λν E = hν = hc λ λ = hmv En = -2.18 x 10 -18 J 1 n2 ΔE = E f inal - E initial ΔE = -2.18 x 10-18 J 1 1 nf 2 ni 2- 12 mv 2 ΔE = q + w n ΔH rxn = q rxn = - q soln = - m soln s soln ΔT soln q rxn = - C cal ΔT w = - P ΔV ΔHorxn = Σ nΔHof (products) - Σ nΔHof (reactants) ΔHorxn = Σ (enthalpies of bonds broken) - Σ (enthalpies of bonds formed) BO = (no. of bonding electrons - no. of antibonding electrons)1 2 KE = Solubility Rules: 1. Most nitrate salts are soluble. 2. Most salts of alkali metals and ammonium cations are soluble. 3. Most chloride, bromide, and iodide salts are soluble. Exceptions: Salts containing Ag+, Pb2+, and Hg22+ ions are insoluble. 4. Most sulfate salts are soluble. Exceptions: Sulfates containing Ca2+, Ba2+, Pb2+ and Hg22+ ions are insoluble. 5. Most hydroxide salts are insoluble. Exceptions: Hydroxides containing alkali metals, Ba2+, Sr2+ and Ca2+ ions are soluble. 6. Most sulfide, carbonate, chromate, and phosphate salts are insoluble. Exceptions: Salts of alkali metals and ammonium cations are soluble.   7. (a) One possible Lewis structure of XeO3 is given. Complete the following table for XeO3. Xe O O O State the electron domain geometry of XeO3. State the molecular geometry of XeO3.Draw an accurate 3-dimensional representation of XeO3. Show the bond polarity of XeO3 with a dipole moment arrow in the 3-dimensional representation. What is the approximate O-Xe-O bond angle? 7. (b) The Lewis structure of CNO- is given. Complete the following table for CNO-. C NO State the electron domain geometry of CNO-. State the molecular geometry of CNO-.Draw an accurate 3-dimensional representation of CNO-. Show the overall (molecular) polarity of CNO- with a dipole moment arrow in the 3-dimensional representation. What is the approximate O-C-N bond angle? -1 8. (a) Draw a Lewis structure with minimized formal charges for BrF3. (b) Draw an accurate 3-dimensional representation of BrF3. (c) State the molecular geometry of BrF3. 2 2 2 22 2 2 2 2 2 3 2 2 9. The chemical formula C2H2Cl2 can represent three different molecules. 3-dimensional representations of each of these molecules are shown below. Label the molecules polar or non-polar in the blank provided under each structure. For each polar molecule, show the polarity with a appropriate dipole arrow over the structure. C C Cl Cl H H C C Cl H Cl H C C Cl H H Cl 9 10. The artif icial sweetener called aspartame has the Lewis structure shown below. The actual structure of the molecule is NOT implied. Complete the following table for aspartame. The 14 carbon atoms have been put in bold print for easier identif ication. N H H C C HH CO O H H C O N H C H C O O C H H HC H H C C C C C C H H H H H (a) What is the hybridization of each N atom in aspartame? (b) How many C atoms in aspartame have sp2 hybridization? (c) What is the approximate C-O-C bond angle at location J in the actual structure? J (d) How many C atoms in aspartame have sp3 hybridization? K (e) What is the approximate O-C-O bond angle at location K in the actual structure? 11. Atoms with expanded octets can form bonds using d atomic orbitals. Three potential ways that d orbitals could overlap with other orbitals are shown below. Label these as the formation of sigma ( ) or pi ( ) bonds in the blank under each figure. 2 2 2 2 2 6