Equations Flashcards
Equation needed for the heat of a phase change.
q = n x ∆H of that specific phase change (e.g, heat of fusion or heat of evaporation)
Note: during a phase change temperature does not change since energy goes into changing the phase.
Equation needed for heat involved in a temperature change (e.g. a liquid heating up but not evaporating)
q = mc∆T
c = specific heat C = heat capacity = cm
therefore q = C∆T too
ideal gas law
PV = nRT
equation used when comparing two scenarios of one gas
P1V1 / T1 = P2V2 / T2
Van der Waals equation for non ideal gases
two corrections involving a and b
a: correction for intermolecular forces experienced at high pressures and low volumes. a is larger for molecules with stronger IMF’s such as hydrogen bonding
b: correction for gases taking up space. b is bigger for bigger gases
grahams law of effusion
effusion rate A molar mass A
——————– = square root of ————–
effusion rate B molar mass B
Thermodynamic equation relating ∆G° and K (at equilibrium). And the equation relating ΔG and Q (not at equilibrium)
At eq: ∆G° = -RTlnK
Not at eq: ΔG = ∆G° + RTlnQ
pH calculation and [H+] calculation
[H+] = 10^ −pH
pH = -log[H+]
Calculation for Gibbs free energy (thermodynamics)
ΔG = ΔH - TΔS
another equation to know is
ΔH = ΔE - PΔV
The Henderson-Hassalbalch equation
pH = pka + log (base form / acid form)
note if we are using a buffer with a base and its conjugate acid (instead of acid / conj. base)
pOH = pKb + log (acid form / base form)
formula used to determine how much base to add to an acidic solution (or vice versa) to completely neutralize it.
[A] x VA = [B] x VB
V is volume
this is the equation used in titrations to determine the unknown solutions concentration
equation to find the ∆G° from a galvanic cell
∆G° = -nFE°
the equation to find E of a cell when not at standard conditions = the Nernst equation. What does it correct for?
derived from ΔG = ΔG° + RTlnQ (replacing G’s with -nFE and rearranging)
E = E° - (RT/nF) lnQ
note that the Nernst equation is with a (-) sign
Nernst = negative
the delta G equation has a (+) sign
finding coulombs from current
Q = It
Q = coulombs of charge (electrical energy) I = current (C/s) t= seconds
what is Avogadro’s number?
The number of particles / entities of any substance in one mole of that substance
6 x 10^23
in terms of the atom, what does A, Z, and N represent?
Z = atomic number = number of protons A = atomic mass = number of P + N N = number of neutrons
A = N + Z
What are the effects of A, N, and Z in all 5 types of radioactive decay?
Z N A
Alpha: -2 -2 -4 (emission of helium)
Beta (-) +1 -1 0 n –> p + electron
Beta (+) -1 +1 0 p —> n + positron
electron -1 +1 0 p + electron —> n
capture
gamma 0 0 0 X(excited) —> x (chill)
what is the equation for formal charge?
FC = Valence e - lone pair e - number of bonds
what is the equation of Zeff?
Zeff = Z - S
Z = atomic number S = shielding electrons (take all e and subtract valence e)
true or false, intermolecular force trend goes
ion - ion > ion - Dipole > H-bond > D-D > induced dipole > instantaneous dipole (London dispersion)
True!! all ionic interactions beat H bonds. H bonds are the strongest in most organic situations
true or false, periodic trends
EA, EN, IE all increase up and to the right
acidity increases down and to the right
radius increases down and to the left
true
F-O-N-Cl-Br-(I=S)-C=H
note that iodine and Sulphur have similar electronegative
how do you calculate the delta H (standard) of a reaction?
Heat of formation products - Heat of formation reactants
First law of thermodynamics
the energy in the universe is constant
∆E (system) = Q - W
This equation puts everything in terms of the system
Q > 0 : heat is absorbed BY the system
Q < 0 : heat is release BY the system
W > 0 : work is done BY the system
W < 0 : work is done ON the system
true or false, spontaneous reactions have a positive ∆S
true, this is law 2 of thermodynamics
what is true of the following processes
isothermal
isochoric
isobaric
adiabatic
isothermal –> temperature does not change therefore P varies with 1/V (inversely proportional)
Isobaric –> pressure does not change (V varies with T)
Isochoric –> volume does not change ( P varies with T)
Adiabatic –> there is no heat exchange
Avodardo’s law says the V varies with moles. At STP what is true?
one mole of gas takes up 22.4 litres of space
therefore for n moles
Vgas at STP = n (22.4)
true or false, for an isothermal, isochoric, or isobaric process, we can hold one variable constant and manipulate PV=nRT. This lets us examine before and after situations. E.g.
isothermal: P1V1 /nRT1 = P2V2 / nRT2
temp is constant and moles should be consant therefore
P1V1 = P2V2
what is the equation for an isochoric process?
P1 / T1 = P2/ T2
in all iso processes, one variable is fixed. What is the combined gas equation when none are fixed and ONLY moles stays constant?
P1V1 / T2 = P2V2 / T2
What is Van Der Waals equation?
Corrects for problems in PV = nRT
first term corrects for IMF’s
second term corrects for mass / volume taken up by the gas
To find the reaction rate of the equation
2A + B –> C
what two equation involving changing concentration can we use?
- 1/2 x ∆ [A} or -∆[B] or \+ ∆[C]
note that we take the inverse of the coefficient if there is one!!!
formula for pH
pH = - long [H+]
pOH = - log [OH]
true or false, at 25 degrees
Kw = [H+][OH-] = 1.0 x 10^-14
true, only temperature can alter Kw
additionally at 25 degrees
pH + pOH = 14
and KaKb = Kw
what is the calculation for pKa?
pKa = -log Ka
where Ka = [A-][H+] / [HA]
degree of unsaturation of chemical compound
2n + 2 - x
d = —————
2
where n is the number of carbons and x is number of hydrogens and any monovalent atom (halogens)
oxygen is ignored
for every nitrogen we add one carbon and on hydrgen
what is the degree of unsaturation of..
C4H6O
C3H5Br
C5H7N
C4H6O = 2(4) + 2 - 6 / 2
8 + 2 - 6 = 4/2 = 2
C3H5Br = 1
C5H7N
2(5) + 2 - 7 / 2 if no nitrogen was there but instead
2(6) + 2 - 8 / 2 = 3
