Chemistry Exam 1 Practice
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Chemistry Exam 1 Practice

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Questions and Answers

What is the value of Avogadro’s number?

  • 3.00 x 10^8
  • 1.6726 x 10^-27
  • 6.022 x 10^23 (correct)
  • 9.1094 x 10^-31

    • Which constant represents the speed of light?

  • -1.60218 x 10^-19 C
  • 1.097 x 10^7 1/m
  • 3.00 x 10^8 m s^-1 (correct)
  • 6.626 x 10^-34 J s

    • How does the mass of a neutron compare to that of a proton?

  • They are identical in mass.
  • The mass of a neutron is irrelevant.
  • The neutron is heavier than the proton. (correct)
  • The neutron is slightly lighter than the proton.

    • What is the relationship between Kelvin and Celsius at absolute zero?

    <p>0 K corresponds with -273.15°C.</p> Signup and view all the answers

    What is the value of the gas constant (R)?

    <p>0.08206 L atm mol^-1 K^-1</p> Signup and view all the answers

    What is the molecular geometry of the astatine atom in Br4At?

    <p>Tetrahedral</p> Signup and view all the answers

    What is the electron geometry around the nitrogen atom if it shows trigonal planar geometry?

    <p>Trigonal planar</p> Signup and view all the answers

    How many sigma bonds are present in the Lewis structure being referenced?

    <p>3</p> Signup and view all the answers

    Which of the following statements is true regarding the polarity of the indicated molecules?

    <p>Only molecule A is nonpolar.</p> Signup and view all the answers

    What is the molecular formula for the ionic compound formed by calcium and the arsenate ion?

    <p>Ca3(AsO4)2</p> Signup and view all the answers

    What type of intermolecular force would be present between two identical molecules?

    <p>London dispersion forces</p> Signup and view all the answers

    Is the arsenate ion polar?

    <p>Yes, it is polar</p> Signup and view all the answers

    What formal charge would be indicated for a neutral atom in a Lewis structure?

    <p>0</p> Signup and view all the answers

    Which bond is likely to be the longest bond on average?

    <p>C-C bond</p> Signup and view all the answers

    What is the electron geometry around the nitrogen atom?

    <p>Tetrahedral</p> Signup and view all the answers

    What is the expected bond angle in a tetrahedral molecular geometry?

    <p>109.5 degrees</p> Signup and view all the answers

    What is the hybridization state of the carbon indicated with an arrow?

    <p>sp2</p> Signup and view all the answers

    When considering molecular geometry, what would the bond angles around an atom with trigonal planar geometry generally be?

    <p>120 degrees</p> Signup and view all the answers

    Which angle is deduced to be larger, the C-O-C angle or the H-P-H angle?

    <p>H-P-H</p> Signup and view all the answers

    Which of the following correctly describes the Lewis structure for SNCl2+?

    <p>S has one lone pair</p> Signup and view all the answers

    What is necessary for full credit when solving math problems on the exam?

    <p>Work must be shown along with the final answer.</p> Signup and view all the answers

    Which items must be stored properly during the exam?

    <p>Electronic devices, except for a calculator.</p> Signup and view all the answers

    How much time is allocated for completion of the exam?

    <p>50 minutes</p> Signup and view all the answers

    What is required when reporting answers on the exam?

    <p>Both correct units and number of significant digits must be included.</p> Signup and view all the answers

    What must students do if they want to ask a question during the exam?

    <p>Only ask for clarification.</p> Signup and view all the answers

    Where should scratch work or additional calculations be recorded?

    <p>On the back of the exam paper only.</p> Signup and view all the answers

    What must students do to affirm their adherence to the University Honor Code?

    <p>Sign the honor pledge on the exam sheet.</p> Signup and view all the answers

    What happens to an answer without accompanying work, regardless of its correctness?

    <p>It will be awarded zero points.</p> Signup and view all the answers

    What is the relationship between energy, frequency, and Planck's constant in photon interactions?

    <p>E = hν</p> Signup and view all the answers

    What is the correct equation to calculate the molar mass of a compound given its empirical formula mass?

    <p>molar mass = empirical formula mass × n</p> Signup and view all the answers

    Which formula represents the relationship between pressure, volume, and temperature in a gas?

    <p>PV = nRT</p> Signup and view all the answers

    What is the empirical formula's molar mass if an empirical formula has a mass of 12 g/mol, and n equals 2?

    <p>24 g/mol</p> Signup and view all the answers

    What value would indicate a pure covalent bond based on electronegativity difference?

    <p>0</p> Signup and view all the answers

    Which equation calculates the kinetic energy of an electron?

    <p>KE = 1/2 mv²</p> Signup and view all the answers

    How is the formal charge of a molecule calculated?

    <p>Formal charge = Ve− − (Be− + LPe−)</p> Signup and view all the answers

    What is the correct relationship for calculating the equilibrium constant from the concentrations of reactants and products?

    <p>K = [products]/[reactants]</p> Signup and view all the answers

    What is the formula used to determine the fraction of ions in a solution i.e., the percentage ionization?

    <p>%ion = ([H₃O⁺]/[HA]) × 100</p> Signup and view all the answers

    What is the definition of the concept of effective nuclear charge (Zeff)?

    <p>Zeff = Z - S</p> Signup and view all the answers

    Study Notes

    Exam 1 Practice

    • The average score on the exam was 72%
    • Students should treat this practice exam like a real exam and time themselves for 50 minutes
    • Only a calculator and a periodic table and formula sheet are allowed
    • Use pencil, write legibly, and show all work and calculations
    • Answers without accompanying work receive zero points
    • Report answers with the correct units and significant figures
    • Clarification questions are allowed, but no help with questions
    • Any corrections to the exam will be written on the board and announced
    • Scratch work should be done on the back page and clearly labeled
    • The honor code requires students to acknowledge that they have not given or received any assistance on the exam

    Molecular Formulas and Names

    • Na2Se: Sodium Selenide
    • Nickel (II) Carbonate: NiCO3
    • Dinitrogen Trioxide: N2O3
    • (NH4)3P: Ammonium Phosphide
    • Pb(CrO4)2: Lead (II) Chromate

    Calcium Arsenate

    • The formula for Calcium Arsenate is Ca3(AsO4)2
    • The arsenate ion is polar
    • The most stable resonance structure for the arsenate ion is the one with the negative charges on the oxygen atoms that are not double bonded to the phosphorus

    Molecular Geometry

    • The molecular geometry around phosphorus is tetrahedral
    • The C-O-C angle is larger than the H-P-H angle
    • The electron geometry around the nitrogen is tetrahedral
    • The N-H bond is the longest bond on average
    • The hybridization around the carbon marked with an arrow is sp3
    • The N - H bond is formed by the overlap of an sp3 and an s orbital
    • The C - C bond is formed by the overlap of an sp3 and an sp3 orbital
    • Four unhybridized p orbitals are used for bonding in this molecule

    SNCl2+

    • The Lewis structure for SNCl2+ has 26 valence electrons
    • There is a formal charge of +1 on the sulfur atom and a formal charge of -1 on one chlorine atom

    Br 4At

    • The VSEPR-3D model shows the bromine atoms in a square planar arrangement around the astatine
    • The electron geometry around the astatine is square planar
    • The molecular geometry around the astatine is square planar
    • The bond angles around astatine are 90 degrees
    • The molecule is nonpolar

    Phosphorus and Chlorine Molecule

    • There is a formal charge of +1 on the phosphorus atom and a formal charge of -1 on one chlorine atom
    • The phosphorus atom has a tetrahedral molecular geometry
    • The molecule is polar

    Intermolecular Forces

    • Hydrogen bonding and dipole-dipole forces are present between molecules with hydrogen bonding (like water)
    • Dipole-dipole forces are present between polar molecules
    • London dispersion forces are present between all molecules

    Polarity

    • Both Molecule A and Molecule B are polar

    Nitrogen Molecule

    • There are 5 sigma bonds in the given structure
    • There are 2 pi bonds in the given structure
    • The electron geometry around nitrogen is trigonal planar
    • The resonance structure that accounts for the trigonal planar geometry around the nitrogen atom shows a double bond between the nitrogen and one of the oxygens, a single bond between the nitrogen and the other oxygen, and a lone pair on the positively charged nitrogen

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    CHEM131 Practice Exam 1 PDF

    Description

    Prepare for your Chemistry Exam 1 with this practice quiz that mimics the exam conditions. Covering key topics such as molecular formulas and naming compounds, this quiz is designed to enhance your understanding and performance. Remember to time yourself and show all work for complete credit.

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