General Chemistry

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Anonymous
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140772
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General Chemistry
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2012-03-11 22:58:21
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Gen Chem equations
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  1. Convert between F and C (when C = 0, F = 32)
    TF = 9/5TC + 32
  2. Energy of electron jumping
    • E relates to Z2/n2, where Z = nuclear charge
    • E = constant (1/nf2 - 1/ni2)
    • So, jump from higher initial ni = more E, farthest = most energy
  3. Quantum numners
    number of e in a level
    • Number of e in an level = 2n2
    • First QN = n = average radius, level
    • Second QN = l = n-1---> 0
    • Third quantum number = ml = +/1 all of l values
    • 4ths = ms = spin
    • L = shape, 0 = s, 1 = p, 2 = d, 3 = f
    • ml = axis in shape, for l = 0, ml = 0 = sphere
    • for l = 1, ml = -1, 0, 1 = 3 lobes for p
    • Each lobe = 2 electrons
    • So, s = 2, p = 6, d = 10
  4. Z effective, periodic trends
    • Zeff = nuclear pull = core e- + protons = 2 + protons so Z effective increases as go right, and decreases down
    • EA, IE, EN all increase as you go right and up
    • Atomic radius = opposite
  5. Series for absorption
    Photoelectric effect
    • To n=2 = Balmer
    • To n = 1 = Lyman
    • To n = 3 Paschen
    • hv (photon) = work + KE
  6. Radioactive Decay
    • Remember charge and mass must match on each side
    • Alpha decay = losing helium
    • Beta decay = losing electron, so neutron converted to proton
    • Positron decay = losing positive electron so proton converted to neutron
  7. Equilibrium constant
    Forward, reverse rate
    Keq Change
    Qrx
    Volume
    • Keq = P/R at eq
    • forward rate = k1[R], reverse = k2[P]
    • So, Keq = k1/k2
    • Stoichimetric coeff = exponents
    • Keq only changes with temperature, nothing else
    • Qrx = P/R at any old time
    • Be careful of volume with problems, doesn't always cancel in P/R
  8. How to solve Keq problem
    When to ignore +x and -x
    • Always set up as + and -x, solve for Keq
    • Note, adding up E components in gas proble
    • Ignore x if,
    • all reactants and Keq = <10-3
    • all products and Keq = >103
    • R and P and K = 1
  9. Complex equilibirum
    LeChatleir's
    • Happens if product of 1 rxn = reactant of second
    • Multiple coeff of 1 rxn so numbers match, and do Keqn to get new Keq for the altered one
    • Next to get whole Keq multiply this new Keq x other rxn's Keq
    • LeChat; rxn goes back to eq if add or change something. Consider heat, endo exo, moles of gas etc
  10. Molar solubility
    Ksp
    Common Ion Effect
    • MS = true measure of solubility = max moles per volume
    • Ksp = solubility product = [P1][P2]
    • Solve like Ice box, +x, -x, but also, coeff = exponents
    • x itself = molar solubility
    • if question asks for moles dissolved after eq, do n times coeff, b/c x is in solubility/mole
    • CIE = like reverse le chatlier's, can represent in ICE box
  11. Arhenius Acid, B-L, Lewis
    Neutral Water, 14
    Ka
    Kb
    Conj pair
    • Arhenius A = produces H3O in water
    • B-L = proton doner
    • Lewis A = lone pair acceptor
    • Neutral at 25 C, pH = pOH, 7 = 7
    • Ka, larger = higher P/R = better acid
    • pka = -log Ka
    • Kb, larger = better base
    • pkb = -logKb
    • For conjugate pair, pKa + pKb = 14
  12. Strong, weak, very weak acids, bases
    Typical strong acids, bases
    Haloacid trend
    Oxyacid anatomy
    • Strong, K>1, pka<0
    • Weak, 10-14<K<1, 0<pka<14
    • Veryweak, K < 10-14, pka > 14
    • Same trend for bases, except, Kb and pKb
    • Strong acids = oxacids and haloacids
    • Strong bases = carbides (Li-Butyl), amides (Li Dia, NR2), alkoxides, hydrides, hydroxides
    • Haloacids, opp of FONClBrISH, I>Br>Cl>F
    • Oxyacid, more O, more EN central atom = more acidic
    • C.A.Ph.AlcAlpha, 5,10.15.20
  13. Logarithms
    Equation for pH when you know pKa and HA
    Equation for pOH when you know pKb and A-
    • log (axb) = loga + logb
    • log (a/b) = loga - logb
    • log 2 = .3
    • log 3 = .48
    • pH = 1/2pKa - 1/2log[HA]
    • pOH = 1/2pKb - 1/2log[A-]
    • note, HA or A must be > Ka or Kb
    • and pK must be 2<pK<12
  14. pH and pka
    Amino acids
    HH equation
    • if pH < pKa, protonated, conj acid presides
    • if pH > pKa, deprotonated, conj base presides
    • AA, C.A., pka = 2-3, so deprot, NH3, pka = 9-10, prot
    • if conj a and conjb present
    • pH = pKa + log([A]/[HA])
  15. Buffer range
    Recipe for buffer
    • Buffer range when A- = HA of conjugate pair
    • But also, range in pH = + and -1 from pKa
    • Since HH says pH = pKa + log([A]/[HA]), then that means between when A-/HA = 10/1---1/10
    • Recipe; 1/2 HA + 1/2A of conj pairs OR
    • 1/2 A + 1SA OR 1/2 HA + 1 SB
    • SA and SB will react completely, should be unrelated to original acid or base
    • Pick HA or A with pka etc near pH you want
  16. Titrations, SA + SB
    pH before titration
    pH before eq point
    pH at eq point
    pH after eq point
    • SA + SB, equivalence = when equal moles added = pH 7 aways.
    • SA into WB or SB into WA
    • if second, when 1/2 equivalent added = buffer, at 1 equivalent, pH > 7 because produce all conjugate base
    • opposite for SA into WB
    • To find pH of weak acid before titration = 1/2pKa - 1/2log[HA]
    • Before eq point, near buffer zone, use HH. At exactly 1/2 eq point, pH = pKa
    • At eq point, pH = 1/2(pka + pH titrant)
    • After eq point, pH = 14 - pOH, pOH = -log(molarity of SB * each new ml added/total liquid added so far)
  17. Indicators
    • Indicators, H-IND -> H+ + IND-
    • Treat like HA and A of buffer
    • Color changes at eq point
    • pH solution = pKaind +log[Ind/Hind]
    • Choose pkA indicator that is + or -1 from equivalence point of acid and base titrating
  18. Best ideal gas
    van der waals gas law
    • Best ideal gas = decrease collisions= low P, increase temp so IMF overcome
    • (P+an2/V2)(V-nb)=nRT, so Pressure usually less or more depending on repel or attract, and V is usually less
    • Usually real gas behaves in a way to fall short of any predictions of Ideal Gas Law
  19. Avogadro's Law
    Boyle's Law
    Charle's Law
    Partial pressure
    liquid pressure
    • V/n = V/n
    • PV=PV
    • V/T = V/T
    • PP = mole fraction x total pressure
    • LP, difference in heights = density x gravity x change h
    • absolute = Patm + pgh
  20. Gas speed, kinetic energy, trends
    root mean squared speed
    Diffusion, effusion, iffusion
    Isotropic enrichment
    • 1/2mv2 = 3/2RT
    • Use R as 8.3 if includes speed
    • v2/v1 = aqrt(m1/m2) = sqrt(T2/T1)
    • rms speed = sqrt (3RT/m)
    • lighest gas diffuses fastest
    • effusion, gas withmore conc, lighest = fastest
    • Can separate isotopes based on weight, lightest effuses first
  21. o

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