Chem 115A Final Practice Exam Flashcards

Chemical Reaction and Stoichiometry

  • Reaction:
    2C8H{18}(l) + 25O2(g) \rightarrow 16CO2(g) + 18H_2O(g)
    \Delta H = -10,900 \text{ kJ}
  • To find gallons of octane to generate 375,000 kJ, consider:
    • 1 gal = 3.78 L
    • Octane density = 0.703 g/mL
  • Limiting Reactant Determination:
    • Given: 30.0 g of propane (C3H8) and 75.0 g of oxygen.
  • Balancing Reactions:
    • Ca(OH)2(s) + H2S(g) \rightarrow
    • Na2CO3(aq) + H_2S(g) \rightarrow

Gas Laws

  • Automobile Air Bag:
    • Volume = 66.8 L
    • Temperature = 25°C
    • Nitrogen gas = 77.8 g
    • Find pressure in kPa.
    • (1 atm = 760 torr = 101,325 Pa = 760 mmHg)

Redox Reactions

  • Identify oxidized/reduced atoms, change in oxidation state, and oxidizing/reducing agents:
    • Mg(s) + NiCl2(aq) \rightarrow MgCl2(aq) + Ni(s)
    • PCl3(l) + Cl2(g) \rightarrow PCl_5(s)
    • C2H4(g) + 3O2(g) \rightarrow 2CO2(g) + 2H_2O(g)

Calorimetry

  • Copper block heated to 547°C, dropped into 293g water at 25.0°C, final temp = 45.1°C.
    • Find mass of copper block.
    • Specific heat capacity of copper = 0.383 J/(g*°C)
    • Specific heat capacity of water = 4.18 J/(g*°C)

Molarity and Dilution

  • Molarity of diluted solution:
    • 22.50 mL of 0.025M C{12}H{22}O_{11} diluted to 100 mL

Enthalpy of Combustion

  • Using the table, calculate the enthalpy of combustion of gas and liquid butane.
    • Compound \Delta H_f° (kJ/mol).
    • C4H{10}(g): -126
    • C4H{10}(l): -148
    • H_2O(g): -242
    • H_2O(l): -286
    • CO_2(l): -421
    • CO_2(g): -394

Enthalpy Change

  • Graphite to acetylene reaction: 2 C(\text{graphite}) + H2(g) \rightarrow C2H_2(g)
    • Data:
      • C(\text{graphite}) + O2(g) \rightarrow CO2(g) \quad \Delta H_{rxn} = -393.5 \text{ kJ}
      • 2H2(g) + O2(g) \rightarrow 2H2O(l) \quad \Delta H{rxn} = -571.6 \text{ kJ}
      • 2C2H2(g) + 5O2(g) \rightarrow 4CO2(g) + 2H2O(l) \quad \Delta H{rxn} = -2598.8 \text{ kJ}

Moles Calculation

  • Calculate moles in a block of ice:
    • Length = 60.96 cm, width = 30.50 cm, height = 25.0 cm, density = 0.90 g/ml

Empirical Formula

  • Lucite (Plexiglas):
    • 59.9% C, 8.06% H, 32.0% O.

Ions

  • Determine the number of protons & electrons:
    • Ni^{2+}
    • Se^{2+}
    • C^{+}
    • F^{-3}

Double-Displacement Reactions

  • Predict products and balance:
    • Lithium carbonate + magnesium bromide \rightarrow
    • Iron(II) sulfate + sodium phosphate \rightarrow

Electrolytes

  • Strong, weak, or non-electrolyte solutions:
    • HF
    • HC2H3O_2
    • CH_3OH
    • NH_3

Physical vs. Chemical Changes

  • Classify:
    • Coal burning
    • Ice melting
    • Mixing chocolate syrup with milk
    • Explosion of a firecracker
    • Magnetizing of a screwdriver

Quantum Numbers

  • Match symbols (l, ml, ms, n) to:
    • Orientation of an orbital.
    • Shape of an orbital.
    • Size of an orbital.
    • Electron spin.

Photons

  • Heated lithium atoms emit photons with energy 2.961 x 10^{-19} \text{ J}.
    • Calculate frequency, wavelength.
    • Total energy in 1 mole.
    • Color of emitted light.

Bohr Model

  • Energy of photon when electron in He^{+} moves from n = 5 to n = 2.

Electron Configuration

  • Valence electrons, atom, or electron configuration:
    • Atom: 1s^22s^22p^63s^23p^64s^23d^{10}4p^65s^24d^2
    • Atom: Cu
    • Ion: Na^{+}

Radio Waves

  • FM-95 broadcasts at 9.51 x 10^7 s^{-1}. What is the wavelength?

Atomic Radii

  • Smaller radii than barium atom:
    • Bi, Cs, Mg, Ba^{2+}, Cs^{+}

Bond Energies

  • Total energy to break all bonds in C2H2BrCl.

Lewis Structures

  • Correct Lewis structures:
    • O_2
    • N_2O
    • HOCl
    • CH_3Cl

Triangular Bipyramidal Geometry

  • Which have triangular bipyramidal electron-pair geometry:
    • AlCl_4^{-}
    • ICl_3
    • SnCl_5^{-}
    • SOCl_2
    • TeCl_4

Polar Bonds

  • Most polar bond: C-C, C-H, N-H, O-H, Se-H