Structure and Bonding
Which molecule is nonpolar?
a) NH₃
b) H₂O
c) SO₂
d) CO₂
CO₂
Draw: 2,4-dimethyl-1-penten-3-ol
Vary.
A reaction has ΔH = +85 kJ. On a potential energy diagram, would the products be higher or lower in energy than the reactants? Draw it!
Higher; the reaction is endothermic.
At equilibrium, what is equal?
a) Concentrations of reactants and products
b) Amounts of reactants and products
c) Forward and reverse reaction rates
d) Values of K and Q
c) Forward and reverse reaction rates
Determine the oxidation number of nitrogen in NH₄⁺.
N = −3
Determine the oxidation number of chlorine in ClO₄⁻.
+7
Draw: 3-phenyl-1-propyne
Vary.
A 75.0 g sample of water absorbs 6.27 kJ of heat. If the initial temperature is 22.0°C, what is the final temperature?
q = mcΔT
6270 = (75.0)(4.18)(ΔT)
ΔT = 20.0°C
Tf = 42.0°C
For the reaction:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
Write the equilibrium expression.
K = [NH₃]² / ([N₂][H₂]³)
For the reaction:
2Ag⁺(aq) + Fe(s) → 2Ag(s) + Fe²⁺(aq)
Determine:
a) The oxidation number of Fe before and after the reaction
b) Is Fe oxidized or reduced?
Fe: 0 → +2
Fe is oxidized
Rank the following ions from smallest to largest radius:
Na⁺, Mg²⁺, O²⁻
Mg²⁺ < Na⁺ < O²⁻
Identify the type of organic reaction occurring:
CH₂=CH₂ + Br₂ → CH₂Br–CH₂Br
Addition reaction
A reaction releases 42.5 kJ of heat when 0.250 mol of reactant burns. Calculate the molar enthalpy of combustion.
ΔH = -42.5 kJ / 0.250 mol
ΔH = -170 kJ/mol
A reaction has K = 25 and Q = 5.
Will the reaction shift left, shift right, or remain unchanged?
Q < K
Reaction shifts right.
For the reaction:
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
Identify:
a) The oxidizing agent
b) The reducing agent
c) What is oxidized
d) What is reduced
Oxidizing agent = Cu²⁺
Reducing agent = Zn
Oxidized = Zn
Reduced = Cu²⁺
Complete the following for SF4.
Molecular Geometry???
Polar or Nonpolar???
Consider the following compounds:
Rank them from lowest boiling point to highest boiling point.
Butanal < Butanone < Butan-1-ol < Butanoic acid
Use standard enthalpies of formation to calculate ΔHrxn.
2NO₂(g) + 7H₂(g) → 2NH₃(g) + 4H₂O(l)
Given:
ΔHf°[NO₂(g)] = +33.2 kJ/mol
ΔHf°[NH₃(g)] = -46.1 kJ/mol
ΔHf°[H₂O(l)] = -285.8 kJ/mol
ΔHf°[H₂(g)] = 0 kJ/mol
Products:
2(-46.1) + 4(-285.8) = -1235.4 kJ
Reactants: 2(+33.2) + 7(0) = +66.4 kJ
ΔHrxn = -1235.4 - 66.4
ΔHrxn = -1301.8 kJ
For the reaction:
2SO₂(g) + O₂(g) ⇌ 2SO₃(g) + heat
Predict the effect of each change:
a) Increase temperature
b) Increase pressure
c) Remove SO₃
a) Shift left
b) Shift right
c) Shift right
Given:
Zn(s) → Zn²⁺(aq) + 2e⁻ E°ox = +0.76 V
Cu²⁺(aq) + 2e⁻ → Cu(s) E°red = +0.34 V
Determine:
a) Anode
b) Cathode
c) E°cell
d) Is the reaction spontaneous?
Anode = Zn
Cathode = Cu
E°cell = +1.10 V
Spontaneous = Yes
An atom has the electron configuration:
1s² 2s² 2p⁶ 3s² 3p⁴
a) Identify the element.
b) Give a possible set of quantum numbers for the last electron.
Draw or name all structural isomers (including cis/trans isomers where applicable).
Use Hess’s Law to calculate ΔH for:
2C(s) + 3H₂(g) → C₂H₆(g)
Given:
C₂H₆(g) + 7/2O₂(g) → 2CO₂(g) + 3H₂O(l) ΔH = -1560 kJ
C(s) + O₂(g) → CO₂(g) ΔH = -394 kJ
H₂(g) + 1/2O₂(g) → H₂O(l) ΔH = -286 kJ
ΔH = -86 kJ
For the reaction:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
A 2.00 L container initially contains:
At equilibrium, [NH₃] = 0.60 mol/L.
Calculate Keq.
Keq = [NH₃]² / ([N₂][H₂]³)
Keq = (0.60)² / [(0.90)(1.50)³]
Keq = 0.36 / 3.0375
Keq = 0.119
For the reaction:
ClO₂(aq) + 2OH⁻(aq) → ClO₃⁻(aq) + ClO₂⁻(aq)
Trial 1
[ClO₂] = 0.0150 M
[OH⁻] = 0.0250 M
Rate = 1.30 × 10⁻³ mol/L·s
Trial 2
[ClO₂] = 0.0150 M
[OH⁻] = 0.0500 M
Rate = 2.60 × 10⁻³ mol/L·s
Trial 3
[ClO₂] = 0.0450 M
[OH⁻] = 0.0250 M
Rate = 1.30 × 10⁻³ mol/L·s
Determine:
a) Order with respect to ClO₂
b) Order with respect to OH⁻
c) Rate law
d) Value of k
Order of ClO₂ = 0
Order of OH⁻ = 1
Rate = k[OH⁻]
k = 0.0520 s⁻¹