Equations Flashcards

1
Q

Equation needed for the heat of a phase change.

A

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.

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2
Q

Equation needed for heat involved in a temperature change (e.g. a liquid heating up but not evaporating)

A

q = mc∆T

c = specific heat 
C = heat capacity = cm 

therefore q = C∆T too

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3
Q

ideal gas law

A

PV = nRT

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4
Q

equation used when comparing two scenarios of one gas

A

P1V1 / T1 = P2V2 / T2

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5
Q

Van der Waals equation for non ideal gases

A

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

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6
Q

grahams law of effusion

A

effusion rate A molar mass A
——————– = square root of ————–
effusion rate B molar mass B

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7
Q

Thermodynamic equation relating ∆G° and K (at equilibrium). And the equation relating ΔG and Q (not at equilibrium)

A

At eq: ∆G° = -RTlnK

Not at eq: ΔG = ∆G° + RTlnQ

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8
Q

pH calculation and [H+] calculation

A

[H+] = 10^ −pH

pH = -log[H+]

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9
Q

Calculation for Gibbs free energy (thermodynamics)

A

ΔG = ΔH - TΔS

another equation to know is

ΔH = ΔE - PΔV

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10
Q

The Henderson-Hassalbalch equation

A

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)

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11
Q

formula used to determine how much base to add to an acidic solution (or vice versa) to completely neutralize it.

A

[A] x VA = [B] x VB

V is volume

this is the equation used in titrations to determine the unknown solutions concentration

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12
Q

equation to find the ∆G° from a galvanic cell

A

∆G° = -nFE°

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13
Q

the equation to find E of a cell when not at standard conditions = the Nernst equation. What does it correct for?

A

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

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14
Q

finding coulombs from current

A

Q = It

Q = coulombs of charge (electrical energy)
I = current (C/s)
t= seconds
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15
Q

what is Avogadro’s number?

A

The number of particles / entities of any substance in one mole of that substance

6 x 10^23

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16
Q

in terms of the atom, what does A, Z, and N represent?

A
Z = atomic number = number of protons 
A = atomic mass = number of P + N
N = number of neutrons 

A = N + Z

17
Q

What are the effects of A, N, and Z in all 5 types of radioactive decay?

A

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)

18
Q

what is the equation for formal charge?

A

FC = Valence e - lone pair e - number of bonds

19
Q

what is the equation of Zeff?

A

Zeff = Z - S

Z = atomic number 
S = shielding electrons (take all e and subtract valence e)
20
Q

true or false, intermolecular force trend goes

ion - ion > ion - Dipole > H-bond > D-D > induced dipole > instantaneous dipole (London dispersion)

A

True!! all ionic interactions beat H bonds. H bonds are the strongest in most organic situations

21
Q

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

22
Q

F-O-N-Cl-Br-(I=S)-C=H

A

note that iodine and Sulphur have similar electronegative

23
Q

how do you calculate the delta H (standard) of a reaction?

A

Heat of formation products - Heat of formation reactants

24
Q

First law of thermodynamics

A

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

25
true or false, spontaneous reactions have a positive ∆S
true, this is law 2 of thermodynamics
26
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
27
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)
28
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
29
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
30
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
31
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!!!
32
formula for pH
pH = - long [H+] pOH = - log [OH]
33
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
34
what is the calculation for pKa?
pKa = -log Ka where Ka = [A-][H+] / [HA]
35
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
36
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