CHEM131 Practice Exam 1 PDF

Name: UID: EXAM 1 PRACTICE CHEM131 - SCHECH The average on this exam was a 72%. To get the best use of this study tool, treat it...

Name: UID: EXAM 1 PRACTICE CHEM131 - SCHECH The average on this exam was a 72%. To get the best use of this study tool, treat it like an actual exam. Close your notes, have the periodic table and formula sheet on hand, and set a timer for 50 minutes. See if you can finish in the time allotted and only with the materials provided on the exam. You have 50 minutes for this exam. All electronic devices, except for a calculator, must be stowed properly. You are allowed to use pencil on this exam. Please make sure your writing is dark so that it will be legible when your exam is scanned. For math problems, please show all of your work in the space below the problems, and put a box around your final answer. Work is required for full credit. Any answer (even if correct) without accompanying work will be awarded zero points. Report your answers with the correct units and number of significant digits. These are parts of the answer and points will be deducted if they are not included in the final answer. The only questions that can be asked during the testing period are clarification questions. Neither the proctors, nor myself, are there to check your work or give you a push in the right direction. Time will be kept at the front of the room. Any corrections to the exam will be written on the board and an announcement will be made. ONLY the back of this page should be used for scratch paper. Please label in your question if your work is elsewhere. If we cannot find it, we will not grade it. Please detach the periodic table and list of constants and equations at the end of the exam. University Honor Code Acknowledgment Sign to acknowledge the honor pledge written below (you do not have to write this sentence): I certify that I have neither given nor received assistance of any kind in the completion of this examination. Signature  USE THIS SPACE FOR SCRATCH PAPER Clearly label what question goes with what work HERE AND IN THE QUESTION SPACE ITSELF 1. (10, 2 pts each, no partial) Provide the molecular formula or name for the following names/formulas. Name Formula Na2Se nickel (II) carbonate dinitrogen trioxide (NH4)3P Pb(CrO4)2 2. (7) Calcium and the arsenate ion (AsO 43-, shown below) interact to form an ionic compound. a. (2) What is the molecular formula for the ionic compound that contains calcium and the arsenate ion? b. (2) Is the arsenate ion polar?  Yes, it is polar  No, it is not polar c. (3) The arsenate ion provided above is one of several resonance structures, all of which are listed below. Which of the following resonance structures is the most stable?      3. (16) Consider the structure below, and then answer the following questions. A D   B C a. (2) What is the molecular geometry around the phosphorus? ___________________________________ b. (2) Which angle is larger, the C-O-C angle or the H-P-H angle?  C-O-C  H-P-H  They are the same c. (2) What is the electron geometry around the nitrogen? __________________________________ d. (2) Which bond is the longest bond, on average?  N-H bond (marked A)  C-H bond (marked B)  O-H bond (marked C) e. (2) What is the hybridization around the carbon marked with an arrow ()? _________________ f. (4) What two orbitals overlap to form the… i. N-H bond marked A ___________ and _____________ ii. C-C bond marked D ___________ and _____________ g. (2) How many unhybridized p orbitals are used for bonding in this molecule? _________________ 4. (5) Draw a Lewis structure for SNCl2+. VSEPR 3D is not required for this question. Include all lone pairs and formal charges not equal to zero. Put the number of electrons needed for the structure in the box. Note 1: This molecule has a charge of +1. Note 2: This molecule contains one or more atoms of the following elements: S,N,Cl Note 3: There is only one central atom. Number of electrons: + 5. (10) Shown below the Lewis structure for Br 4At. a. (2) Draw the molecule in VSEPR-3D. Include all lone pairs. Lewis structure VSEPR-3D b. (2) What is the electron geometry of the astatine (At) atom? _____________________________ c. (2) What is the molecular geometry of the astatine atom? _____________________________ d. (2) What are the bond angles around astatine? _____________________________ e. (2) Is the molecule polar?  Yes, it is polar  No, it is not polar 6. (8) Shown below the Lewis structure for a molecule that contains phosphorus and chlorine. a. (2) Draw the molecule in VSEPR-3D. Include all lone pairs. Lewis structure VSEPR-3D b. (2) Indicate the formal charge for each atom in the box directly above the atom – even if the value is zero. c. (2) What is the molecular geometry of the phosphorus atom? _____________________________ d. (2) Is the molecule polar?  Yes, it is polar  No, it is not polar 7. (6) For the molecules below, select all intermolecular forces that would be present between two of the same molecule by placing an X next to the appropriate intermolecular force. (If you choose hydrogen bond,also choose dipole-dipole). 8. (3) Consider the geometry of the two molecules whose Lewis structures are shown below.  Both molecules are polar.  Both molecules are nonpolar.  Molecule A is nonpolar, molecule B is polar.  Molecule A is polar, molecule B is nonpolar. 9. (10) Consider the Lewis structure shown below. a. (2) How many sigma bonds are in this structure? _____________________________ b. (2) How many pi bonds are in the structure? _____________________________ c. (2) What is the electron geometry around the nitrogen atom? _____________________________ d. (4) An experiment showed trigonal planar geometry around the nitrogen atom for this molecule. Draw a resonance structure for this molecule below that would account for this experimental result. Be sure to include all lone pairs and formal charges not equal to zero on your structure. **You need to draw the entire structure, not just the part with the nitrogen.** END OF EXAM CHEM131 – CONSTANTS & EQUATIONS Fundamental Constants: Name Symbol Value Avogadro’s number NA 6.022 x 1023 Mass of an electron me 9.1094 x 10-31 kg Mass of a proton mp 1.6726 x 10-27 kg Mass of a neutron mn 1.6749 x 10-27 kg Gas Constant R 0.08206 L atm mol-1 K-1 Charge on an electron e -1.60218 x 10-19 C Planck’s constant h 6.626 x 10-34 J s Speed of light c 3.00 x 108 m s-1 Rydberg constant R 1.097 x 107 1/m Autoionization constant Kw 1.0 x 10-14 Useful Relationships and Equations: 0 K (exact) = -273.15°C 1 Joule = 1 kg m2 sec–2 cm3 = 1.00 mL 1 in. = 2.54 cm 1 kg = 2.205 lb 1.6605 x 10-27 kg = 1 amu 1 atm = 1.01325 x 105 Pa = 760 torr = 760 mm Hg avg atomic mass = Σ(fractional abundance of isotope)(mass of isotope) Vsphere = 4⁄3 πr 2 c = λν λ = h⁄mv SAsphere = 4πr 2 E = hν = hc⁄λ Ephoton = Φ + KEelectron KE = 1⁄2 mv 2 1 1 1 1 1⁄λ = R ( f 2 − i 2 ) Ephoton = −2.178 × 10−18 J ( f 2 − i 2 ) Zeff = Z − S (n ) (n ) (n ) (n ) molar mass 1 n= formal charge = Ve− − ( Be− + LPe− ) C1V1 = C2V2 empirical formula molar mass 2 P1 V1 P V q = mC∆T PV = nRT n1 T1 = n2 T2 2 2 qsys = -qsoln ° ° ∆H° = Σ n∆Hf,prod − (n∆Hf,react ) q = n∆H° ∆H° = Σ(nBEbroken ) − (nBEformed ) −b ± √b 2 − 4ac [H3 O+ ] x= %ion = × 100 K w = [OH − ][H3 O+ ] 2a [HA] pX = −logX X = 10−pX pH + pOH = 14 Electronegativity di erence Bond Type (EN) 0 Pure covalent 0.1 – 0.4 Non-polar covalent 0.5 – 2.0 Polar covalent >2.0 Ionic  List of Elements (Chemical symbol is alphabetical) Ac Actinium He Helium Ra Radium Ag Silver Hf Hafnium Rb Rubidium Al Aluminum Hg Mercury Re Rhenium Am Americium Ho Holmium Rf Rutherfordium Ar Argon Hs Hassium Rg Roentgenium As Arsenic I Iodine Rh Rhodium At Astatine In Indium Rn Radon Au Gold Ir Iridium Ru Ruthenium B Boron K Potassium S Sulfur Ba Barium Kr Krypton Sb Antimony Be Beryllium La Lanthanum Sc Scandium Bh Bohrium Li Lithium Se Selenium Bi Bismuth Lr Lawrencium Sg Seaborgium Bk Berkelium Lu Lutetium Si Silicon Br Bromine Lv Livermorium Sm Samarium C Carbon Mc Moscovium Sn Tin Ca Calcium Md Mendelevium Sr Strontium Cd Cadmium Mg Magnesium Ta Tantalum Ce Cerium Mn Manganese Tb Terbium Cf Californium Mo Molybdenum Tc Technetium Cl Chlorine Mt Meitnerium Te Tellurium Cm Curium N Nitrogen Th Thorium Cn Copernicium Na Sodium Ti Titanium Co Cobalt Nb Niobium Tl Thallium Cr Chromium Nd Neodymium Tm Thulium Cs Cesium Ne Neon Ts Tennessine Cu Copper Nh Nihonium U Uranium Db Dubnium Ni Nickel V Vanadium Ds Darmstadtium No Nobelium W Tungsten Dy Dysprosium Np Neptunium Xe Xenon Er Erbium O Oxygen Es Einsteinium Og Oganesson Eu Europium Os Osmium F Fluorine P Phosphorus Fe Iron Pa Protactinium Fl Flerovium Pb Lead Fm Fermium Pd Palladium Fr Francium Pm Promethium Ga Gallium Po Polonium Gd Gadolinium Pr Praseodymium Ge Germanium Pt Platinum H Hydrogen Pu Plutonium