BASICS
Determine the moles of Mg in a 2.50 g sample
•n = m/M_r = 0.103 mol.
Predict the shape of NH₃ using VSEPR both electron geometry and the molecular geometry.
Tetrahedral electron geometry; trigonal pyramidal shape.
List three factors that increase reaction rate.
Higher concentration, higher temperature, increased surface area.
Sketch a potential energy diagram for an endothermic reaction.
potential energy of the products are higher than the reactants
Find the oxidation state of S in H₂SO₄.
+6.
Find the relative molecular mass of Mg(OH)₂
58.32
Explain why CO₂ is non‑polar but H₂O is polar.
CO₂ is linear so dipoles cancel; H₂O is bent so dipoles add.
Describe how the Maxwell–Boltzmann distribution changes as temperature increases.
The curve flattens and shifts right; more molecules exceed activation energy.
Determine the enthalpy of reaction for the following:
H2(g) + 1⁄2 O2(g) ---> H2O(g)
H−H (432); O=O (496); H−O (463)
ΔH = −246 kJ
Assign oxidation numbers to Cr and O in Cr₂O₇²⁻
Cr = +6; O = –2.
Define and compare elements and compounds
Elements: a pure substance that cannot be broken down into smaller parts. Compound: a pure substance containing two or more kinds. Atoms are combined in a specific ratio and can be separated chemically
Predict the geometry and bond angles in PCl₅
Trigonal bipyramidal; 90° and 120° angles.
Write the rate law given doubling [A] doubles rate and doubling [B] quadruples rate.
Rate = k[A]¹[B]²; overall order 3.
Calculate ΔG at 298 K for ΔH = –50 kJ mol⁻¹ and ΔS = –100 J mol⁻¹ K⁻¹. Comment on whether this reaction is spontaneous or non-spontaneous.
ΔG = –20.2 kJ mol⁻¹ and spontaneous.
In Zn + CuSO4→ ZnSO4 + Cu, identify the species oxidised and reduced and the oxidising/reducing agents.
Zn is oxidised; Cu²⁺ is reduced. Cu²⁺ is the oxidising agent; Zn is the reducing agent.
What mass of magnesium bromide is formed when 1.00 g of magnesium reacts with 5.00 g of bromine?
Mg + Br2 -> MgBr2
5.75 g
Explain why atomic radii decrease across a period and increase down a group.
Going across a period shrinks atoms- increasing nuclear charge means there more protons compared to electrons - increasing electrostatic attraction. Going down the group, adding shells and increases shielding which decreases the electrostatic attraction from the nucleus to the valence electrons
20.83 g of a gas occupies 4.167 L at 79.97 kPa at 30.0 °C. What is its molecular weight?
1) Solve for the moles using PV = nRT:
n = PV / RT
n = [(79.97 kPa / 101.325 kPa atm¯1) (4.167 L)] / [(0.08206 L atm mol¯1 K¯1) (303.0 K)]
n = 0.13227 mol
2) Divide the grams given (20.83) by the moles just calculated above:
20.83 g / 0.13227 mol = 157.5 g/mol
At what temperature will an endothermic reaction with ΔH = +100 kJ and ΔS = +250 J K⁻¹ become spontaneous?
T = 400K
Write this equation MnO₄⁻ → Mn²⁺ in acidic condition.
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O.
Determine the molecular formula from the percentages by weight and the molecular weight. 65.45% C, 5.45% H, 29.10% O; mol. wt. = 110
C6H6O2
Calculate the energy of a photon with ν = 6×10¹⁴ Hz
E = hν = 3.98×10⁻¹⁹ J
Identify the rate‑determining step and overall equation for the reaction of NO2 with F2. Refer to the print out
Step 1 - rate determining step
Rate = k[NO2][F2]
Describe the role of ionization energy in the Born-Haber Cycle.
Ionization energy is required to remove electrons from gaseous atoms to form cations
Balance each redox reaction in acid solution. ClO3- + Cl- -> Cl2 + ClO2
4 H + + 2 ClO3 - + 2 Cl - -> 2 ClO2 + 2 H2O + Cl2