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A-level Chem - Content to Memorise > Formulae > Flashcards

Formulae Flashcards

1
Q

Moles (n)

A

n=m/Mr

n= mol
m = g

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2
Q

Relative atomic mass

A

∑(isotopic mass x abundance) / 100 (or total abundance)

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3
Q

Relative molecular mass

A

eg. C2H6O

Mr = (2 x 12.0) + (6 x 1.0) + (1 x 16.0) = 46.0

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4
Q

Kinetic Energy (mass spectrometry)

A

KE = 1/2mv^2

KE = kinetic energy, J
m = mass, kg
v = velocity, m s-1

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5
Q

Time of flight

A

t = d/v

t = time of flight, s
d = length of flight tube, m
v = velocity, m s-1

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6
Q

Conc.

A

n=cv

n = mol
c = mol dm-3
v = dm-3

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7
Q

No. of molecules

A

n x 6.022x10^22

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8
Q

Ideal gas equation

A

pV=nRT

P= Pa
V=m3
n= mol
T=K

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9
Q

Atom economy

A

(Mr desired product / sum of Mr of reactants) x 100

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10
Q

Percentage yield

A

(actual yield / theoretical yield) x 100

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11
Q

Enthalpy change

A

q = mcΔT

q = enthalpy change, J
m = mass, g
c = SHC
ΔT = temp change, K

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12
Q

Enthalpy change of a reaction

A

∑energy absorbed (bonds broken) - ∑energy released (bonds made)

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13
Q

Rate of reaction

A

Rate of reaction = amount of reactant used or product formed / time

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14
Q

Equilibrium constant, Kc

A

[D] = conc. of product D (mol dm -3)
d = moles of D (mol)
[A] = conc. of reactant A (mol dm-3)
a = moles of A (mol)

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15
Q

Entropy change of a system

A

ΔS = S (products) - S (reactants)

ΔS = entropy change (J K-1 mol-1)
S = entropy (J K-1 mol-1)

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16
Q

Gibbs free energy change

A

ΔG = ΔH - TΔS

ΔG = free energy change (J mol-1)
ΔH = enthalpy change (J mol-1)
T = temp (K)
ΔS = entropy change (J K-1 mol-1)

17
Q

Temp when ΔG is zero

A

T = ΔH/ΔS

ΔH = enthalpy change (J mol-1)
T = temp (K)
ΔS = entropy change (J K-1 mol-1)

18
Q

Rate equations

A

Rate = rate of reaction (mol dm-3 s-1)
k = rate constant
[A] = conc. of A (mol dm-3)
m = order of A

19
Q

Arrhenius equation

A

k = rate constant
A = Arrhenius constant
Ea = activation energy (J mol-1)
R = gas constant
T = temp (K)

20
Q

Arrhenius equation (log form)

A

k = rate constant
A = Arrhenius constant
Ea = activation energy (J mol-1)
R = gas constant
T = temp (K)

21
Q

Mole fraction of a gas in a mixture

A

no. of moles of gas / total no. of moles of gas in the mixture

22
Q

Partial pressure of a gas in a mixture

A

mole fraction of gas x total pressure of mixture

23
Q

Equilibrium constant, Kp

A

Kp = equilibrium constant
[D] = pD, partial pressure of D (Pa)
d = no of moles of D (mol)

24
Q

EMF of a cell (cell potential)

A

E⦵ cell = E⦵ reduced - E⦵ oxidised

E⦵= V

(with this formula, you do not flip the oxidising electrochemical cells ‘standard electrode potential’)

25
Q

EMF of a cell (cell potential) FROM DIAGRAM

A

E⦵ cell = E⦵ right-hand side - E⦵ left-hand side

E⦵= V

(with this formula, you do not flip the oxidising electrochemical cells ‘standard electrode potential’)

26
Q

Ionic product of water, Kw

A

Kw = [H+][OH-]

Kw = ionic product of water (mol2 dm-6)
[H+] = conc. of H+ ions (mol dm-3)
[OH-] = conc. of OH- ions (mol dm-3)

27
Q

Ionic product of pure water, Kw

A

Kw = [H+]^2

Kw = ionic product of water (mol2 dm-6)
[H=] = conc. of H+ ions (mol dm-3)

28
Q

Calculating pH

A

pH = -log[H+]

29
Q

Calculating [H+] (from pH)

A

[H+] = 10^−pH

30
Q

Acid dissociation constant, Ka

A

Ka = [H+][A-] / [HA]

Ka = acid dissociation constant (mol dm-3)
[H+] = conc. of H+ ions (mol dm-3)
[A-] = conc. of A- ions (mol dm-3)
[HA] = conc. of undissociated acid (mol dm-3)

31
Q

Acid dissociation constant for weak acids, Ka

A

Ka = [H+]^2 / [HA]

Ka = acid dissociation constant (mol dm-3)
[H+] = conc. of H+ ions (mol dm-3)
[HA] = conc. of undissociated acid (mol dm-3)

32
Q

Calculating pKa (from Ka)

A

pKa = -log(Ka)

33
Q

Calculating Ka (from pKa)

A

Ka = 10^-pKa

34
Q

Energy change/absorbed when electrons jump

A

ΔE = hv = hc / λ

ΔE= energy absorbed (J)
h = Planck’s constant
v = freq of light absorbed (Hz)
c = speed of light
λ = wavelength of light absorbed (m)

35
Q

Rf value

A

distance travelled by spot / distance travelled by solvent

36
Q

Percentage uncertainty

A

(uncertainty / reading) x 100

37
Q

Uncertainty on a mean

A

(largest measurement - smallest measurement) / 2

38
Q

Oxidation state of metal in complex ion

A

(total charge of complex ion) - (sum of oxidation states of ligands)

A-level Chem - Content to Memorise (6 decks)

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