Chemistry exam 3

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Chemistry exam 3
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2010-11-15 02:14:36
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Chemistry exam 3
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  1. potential energy
    energy available
  2. kinetic energy
    energy produced by a moving object
  3. thermal energy
    energy associated with the random motion of atoms and molecules
  4. work equation:
    w = -PΔV
  5. conversion for L*atm to J
    101.3J/1 L*atm
  6. thermochemistry:
    study of heat change in chemical reactions
  7. enthalpy of reaction:
    ΔH = H(products) - H(reactants)
  8. expansion:
    system does work on the surroundings
  9. compression:
    work is done on the system by the surroundings
  10. constant pressure equation:
    qp = ΔE + PΔV
  11. enthalpy (H) which is defined by the equation:
    H = E + PV, where E is the internal energy of the system and P & V are pressure and volume
  12. change in enthalpy equation:
    ΔH = ΔE + PΔV
  13. state functions:
    properties that are determined by the start of the system, regardless of how that condition was achieved.
  14. exothermic:
    gives off heat
  15. endothermic:
    heat has been supplied to the system by the surroundings (heat absorbed)
  16. law of conservation of energy:
    energy can be converted from one form to another, but cannot be created nor destroyed.
  17. the first law of thermodynamics:
    the law of conservation of energy.
  18. sign conventions for q and w in equation ΔE = q + w :
    q is positive if for an endothermic rxn and negitive for exothermic ; w is positive for work done one the system by the surroundings and negitive for work done by the system on the surroundings.
  19. heat absorbed/released equation:
    q(J) = s(J / g*C) m (g) Δt (C) without units: q = smΔt or q = CΔt
  20. heat capacity:
    C = ms, where m is mass in grams and s is specific heat.
  21. Hess's Law:
    When reactants are converted to products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps.
  22. what happens to ΔH when you reverse a reaction?
    sign changes
  23. know that ΔH is proportional to the quantity of...
    material present.
  24. standard enthalpy of reaction (ΔHrxn):
    ΔHrxn = [cΔHf(C) + dΔHf(D)] - [aΔHf(A) + bΔHf(B)] or ΔHrxn = #ΔHf(products) - #ΔHf(reactants)
  25. constant V calorimetry: knowing qrxn = - qcal, how do you find Ccal?
    qcal = CcalΔt ; Ccal = qcal/Δt (kJ/C)
  26. constant P calorimetry: example
    q Pb = - q H2O ; q H2O = msΔt
  27. specific heat of H2O:
    4.184 J/g*C
  28. heat of solution (ΔHsoln):
    • definition: heat generated or absorbed when a certain amount of solute dissolves in a certain amount of solvent.
    • equation: ΔHsoln = Hsoln - Hcomponents
  29. heat of dilution:
    heat change associated with the dilution process.
  30. wave:
    vibrating disturbance by which energy is transmitted
  31. wavelength λ (lambda):
    distance between identical points on successive waves. distance/wave
  32. frequency v (nu):
    the number of waves that pass through a particular point in 1 second. wave/time. [v = c/λ given c = 3.00x108 m s-1]
  33. amplitude:
    vertical distance from the midline of a wave to the peak or trough.
  34. speed (u):
    product of its wavelength and frequency. u = λv
  35. 1 Hz =
    1s-1
  36. color of 400 nm:
    violet
  37. color of 500 nm:
    green
  38. color of 600 nm:
    orange
  39. color of 700 nm:
    red
  40. line spectra:
    the light emission only at specific wavelengths.
  41. Planck's constant (h) came from...
    observations known as "black body radiation"
  42. equation using Planck's constant (h):
    E = hv or E=h(c/λ)
  43. "black body radiation":
    refers to an object or system which absorbs all radiation incident upon it and re-radiates energy
  44. photoelectric effect:
    phenomenon in which electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency, called the threshold frequency. Einstein deduced that each photon must possess energy E, given in the equation: E = hv.
  45. wave-particle duality:
    light posses both wavelike and particlelike properties. depending on experiment, light behaves as a wave or as a stream of particles.
  46. photon:
    particle of light.
  47. Einstein's equation:
    E = hv or E = h(c/λ)
  48. Bohr's equation (used to solve for wavelength of a photon emitted during a transition):
    ΔE = RH (1/ni2- 1/nf2)
  49. De Broglie equation (calculate wavelength of particles):
    λ = h/mu [m - mass (kg), u - speed (m/s)]
  50. conversion with J and kg: 1 J =
    1 kg m2/s2
  51. Davisson and Germer demonstrated that electrons do have wavelike properties by...
    directing a beam of electrons through a thin piece of gold foil, they obtained a set of concentric rings on a screen similar to the pattern observed when X rays are used.

  52. Heisenberg principle:
    it is impossible to know simultaneously both the momentum p (mass times velocity) and the position of a particle with certainty.
  53. the probability of finding an electron in a certain region in space is...
    proportional to the square of the wave function, ψ2. The most likely place to find a photon is where the intensity is greatest (where ψ2 is greatest).
  54. angular momentum quantum # l =
    (n-1), if n=3 then l is 0, 1, 2.
  55. magnetic quantum # ml =
    • -l, (-l + 1), .... 0, .... (+l - 1), +l
    • if l=2, then ml = -2, -1, 0, 1, 2. so # of orbitals would be 5.
  56. electronic spin quantum # ms =
    +1/2, -1/2
  57. Stern-Glerch experiment:
    beam of gaseous atoms generated in a hot furnace pass through a nonhomogeneous magnetic field. because spinning motion is completely random, it causes half the electrons to spin one way, and the other half in the opposite direction. this is why ms = +1/2 and -1/2.
  58. Pauli exclusion principle:
    no two electrons in an atom can have the same set of four quantum numbers. (antiparallel spins)
  59. Hund's rule:
    the most stable arrangement of electrons in subshells is the one with the greatest muber of parallel spins.
  60. Aufbau principle:
    says that as protons are added one by one to the nucleus to build up the elements, electrons are similarly added to the atomic orbitals.
  61. paramagnetic:
    contain net unpaired spins and are attracted by a magnet.
  62. diamagnetic:
    do not contain net unpaired spins and are slightly repelled by a magnet.
  63. historical development of the periodic table:
    Newlands noticed that when the elements were arranged in order of atomic mass, every eighth element had similar properties. He referred to this as the law of octaves. His findings only worked through calcuim. Mendeleev and Meyer classification system was a great improvement from Newlands's.
  64. work of Moseley:
    discovered a correlation between what he called atomic number and the frequency of X rays generated by bombarding an element with high-energy electrons.
  65. valence electrons:
    outtermost electrons
  66. core electrons:
    all nonvalence electrons in an atom

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