IB Chemistry Calculations setting out templates
Topic 1 Stoichiometric relationships
SL & HL
Percent composition
M(AB) = ___g/mol
M(A) = ___g/mol
Percentage mass = ___/___ x 100% = ___%
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Empirical and molecular formulae
n(A) = ___g/___gmol-1 = ___mol
n(B) = ___g/___gmol-1 = ___ mol
A___B___
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Ideal gas law
PV = nRT
___ Pa x ___ m3 = ___ mol x 8.314 JK-1 mol-1 x ___ K
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Stoichiometry
aA + bB cC + dD
or / orn(A)
= m/M
= ___g / ___ g/mol
= ___mol A / 1 mol gas : 22.7dm3
X : ___dm3
∴X = ____ mol A / n(A)
= CV
= ___mol/dm3 x ___ dm3
= ___ mol A
a mol A : c mol C
___ mol A : X
∴X = ____ mol C
or / orm(C)
= nM
= ___ mol x ___ g/mol
= ___ g C / 1 mol gas : 22.7dm3
___ mol C : X
∴X = ____ dm3 C / C(C)
= n/V
= ___mol / ___ dm3
= ___ mol/ dm3 C
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Topic 4 Chemical bonding and structure
HL only
Formal charge
First draw Lewis dot structure
FC (___) = valence e- – ½ bonding e- – non-bonding e-
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Bond order
First draw Lewis dot structure
Bond order = total number of bonding pairs/total number of positions
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Bond calculations
Ephoton = hf
v = fλ
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Topic 5 Energetics and thermochemistry
SL & HL
Heat of reaction and enthalpy
aA + bB cC + dD
Q = mcT
= ___ g x 4.18Jg-1ᵒC-1 x ___ᵒC
= ___ kJ
H = Q/n
= ___kJ/___moles = ___ kJ/mol
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Hess’ Law
aA + bB cC + dDH = ___ kJ (reverse etc…)
aA + bB cC + dDH = ___ kJ (X2 etc…)
______
aA + bB cC + dDH = ___ kJ
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Enthalpy of formation
aA + bB cC + dD
ΣΔHoproducts = (c x ____) + (d x ___) = ___ kJ
ΣΔHoreactants = (a x ___) + (b x ___) = ___ kJ
ΔHoformation = ΣΔHoproducts – ΣΔHoreactants = ______- ______= ______kJ
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Enthalpy of combustion
aA + bB cC + dD
ΣΔHoproducts = (c x ____) + (d x ___) = ___ kJ
ΣΔHoreactants = (a x ___) + (b x ___) = ___ kJ
ΔHocombustion = ΣΔHoreactants – ΣΔHoproducts = ______- ______= ______kJ
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Bond enthalpies
EQUATION DRAWN IN STRUCTURAL FORMULA FORM:
aA + bB cC + dD
Bonds broken = (a x ___) + (b x ___) = ___ kJ
Bonds formed = (c x ____) + (d x ___) = ___ kJ
ΔHo = ΣΔHoreactants – ΣΔHoproducts = ______- ______= ______kJ
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HL only
Born Haber cycles
M+(g) + X(g)
↑HIE HEA
M(g) + X(g)
↑HatmXM+(g) + X-(g)
M(g) + 1/2 X2(g)
↑HatmM
M(s) + 1/2 X2(g) Hlat
Hf
MX(s)
Hf = HatmM + HatmX + HIE + HEA - Hlat
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Enthalpy of solution and hydration
M+(g) + X-(g)
Hhyd
Hlat M+(aq) + X-(aq)
Hsol
MX(s)
Hlat = Hsol - HhydX- - HhydM+
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Entropy
aA + bB cC + dD
ΣΔSoproducts = (c x ____) + (d x ___) = ___ J/Kmol
ΣΔSoreactants = (a x ___) + (b x ___) = ___ J/Kmol
ΔS⁰ = ∑ ΔS⁰ (products) - ∑ ΔS⁰ (reactants) = ______- ______= ______J/Kmol
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Gibbs free energy from individual values
aA + bB cC + dD
ΣΔGoproducts = (c x ____) + (d x ___) = ___ kJ/mol
ΣΔGoreactants = (a x ___) + (b x ___) = ___ kJ/mol
ΔG⁰ = ∑ ΔG⁰ (products) - ∑ ΔG⁰ (reactants) = ______- ______= ______kJ/mol
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Gibbs free energy from entropy and enthalpy
aA + bB cC + dD
ΔG⁰ = ΔH⁰ - TΔS⁰ = _____ - ______= ______kJ
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Topic 6 Chemical kinetics
SL & HL
Reaction rate
aA + bB cC + dD
Rate = Δ[P]/t or Δ[R]/t = _____ mol dm-3 s-1
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HL only
Rate equation
aA + bB cC + dD
When [B] is kept constant [A] is _____.Therefore the order of reaction with respect to A is ____.
When [A] is kept constant [B] is _____. Therefore the order of reaction with respect to B is ____.
rate = k[A]?[B]?
Units of k = (mol.dm-3s-1) / order of reaction value x (mol.dm-3)
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Activation energy
ln(k) = Ea/RT + lnA
(Graph ln(k) by 1/T in Kelvin by first making a table if not already done)
Gradient = Ea/R
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Topic 7 Equilibrium
SL & HL
Only writing the equilibrium constant
aA + bB ⇌ cC + dD
Kc = [C]c[D]d / [A]a[B]b (at equilibrium)
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HL only
Reaction quotient
aA + bB ⇌ cC + dD
Q = [C]c[D]d / [A]a[B]b (NOT at equilibrium)
Q is >/< K therefore reaction moves to the left/right.
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The equilibrium constant
aA + bB ⇌ cC + dD
[A] / [B] / [C] / [D]R / a / b / c / d
I
C
E
Kc = [C]c[D]d / [A]a[B]b
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Gibbs free energy and equilibrium
∆G° = -RTlnK
K is >1 therefore favourable etc….
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Topic 8 Acids and bases
HL only
Calculating pH for weak acids and bases
HA(aq) ⇌ H+(aq) + A-(aq)
[H+]2 = [HA]Ka
pH = - log [H+(aq)] = ____
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Topic 9 Redox processes
SL & HL
Balancing redox half equations
Step 1MO M (balance atoms besides H and O)
Step 2 2+ 0(oxidation states)
Step 3 MO + 2e- M (balance electrons)
Step 4 MO + 2e- + 2H+ M (balance charges with H+)
Step 5 MO + 2e- + 2H+ M + H2O (H2O for final balancing)
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Combining redox half equations
Step 1M MO + e- Oxidation
NO + e- NReduction
Step 2 M MO + e- Oxidation multiplied by ____
NO + e- NReduction multiplied by ____
Step 3 NO + M + e- MO + N + e- Add
Step 4 NO + M MO + N Simplify
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HL only
Determining cell potentials with E⁰ values
A+ + e- ⇌ A E⁰=____
B+ + e- ⇌ B E⁰=____
Write and reverse the least positive value
A+ + e- A E⁰=____
B B+ + e- E⁰= (-)____
Add
A+ + B A + B+ E⁰= ____
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Products of electrolysis
Ions present:
A+, B+, H2O
A+ + e- ⇌ A E⁰=____
B+ + e- ⇌ B E⁰=____
½O2(g) + 2H2(aq) + 2e- ⇌ H2O(l) E⁰= + 1.23
H2O(l) + e- ⇌ ½H2(g) + (aq) + OH-(aq)E⁰= - 0.83
Cathode: (take most positive)
A+ + e- A E⁰=____
H2O(l) + e- ⇌ ½H2(g) + (aq) + OH-(aq)E⁰= - 0.83
Anode: (take most positive)
B B+ + e- E⁰= (-)____
H2O(l) ⇌ ½O2(g) + 2H2(aq) + 2e-E⁰= - 1.23
Final equation: (add)
E⁰=____
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Determining cell potentials with Gibbs
If necessary, setting out as above to work out E⁰, then
ΔG⁰ = -nFE⁰
or
E = E⁰ – (RT/nF)lnQ
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Quantitative electrolysis
Q = It
Follow stoichiometry setting out.
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Topic 11 Measurement and data processing
SL & HL
Percent error
Percent error = ((Theoretical result - experimental result)/Theoretical result) x 100%
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Propagation of uncertainty
Add uncertainties for + and - . Add percent uncertainties for x and divide. Don’t forget significant figures. Final absolute uncertainty has only 1 sig fig.
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Index of Hydrogen Deficiency
For CcHhNnOoXx
IHD = (0.5)(2c+2-h-x+n)
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