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