Paper 1: Inorganic and Physical Chemistry

In a time-of-flight mass spectrometer, all ions are given the same kinetic energy. Explain why ⁸¹Br⁺ ions reach the detector after ⁷⁹Br⁺ ions.

The mass spectrum of chlorine gas, Cl₂, has peaks at m/z 70, 72 and 74 in the ratio 9 : 6 : 1. Explain these peaks. (³⁵Cl : ³⁷Cl = 3 : 1)

The first five ionisation energies of element X (kJ mol⁻¹) are 578, 1817, 2745, 11 577, 14 842 (data are illustrative, written for this paper). Deduce the group of X and explain.

A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Calculate its empirical formula.

25.0 cm³ of 0.100 mol dm⁻³ NaOH was neutralised by 21.40 cm³ of sulfuric acid. Calculate the concentration of the sulfuric acid.

Calculate the percentage atom economy for making ethanol by fermentation: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. (Mr: glucose 180.0, ethanol 46.0)

State and explain the shape and bond angle of an ammonia molecule.

Explain why hydrogen fluoride has a higher boiling point than hydrogen chloride.

Explain why magnesium conducts electricity.

In a calorimetry experiment, 0.0250 mol of acid reacted with alkali in 50.0 g of solution. The temperature rose by 6.5 K. Calculate the enthalpy change per mole of acid. (c = 4.18 J g⁻¹ K⁻¹)

Use mean bond enthalpies to calculate ΔH for CH₄ + 2O₂ → CO₂ + 2H₂O(g). (kJ mol⁻¹: C–H 413, O=O 498, C=O 805, O–H 464)

Explain, using the Maxwell–Boltzmann distribution, how a catalyst increases the rate of reaction.

1.00 mol H₂ and 1.00 mol I₂ were sealed in a 1.00 dm³ flask. At equilibrium, 1.56 mol HI was present. H₂ + I₂ ⇌ 2HI. Calculate Kc.

State and explain the effect of increasing pressure on the position of this equilibrium.

Explain why a catalyst does not change the value of Kc.

Give the oxidation states of manganese in MnO₄⁻ and chromium in Cr₂O₇²⁻.

Write half-equations for the reduction of MnO₄⁻ to Mn²⁺ in acid and the oxidation of Fe²⁺, and combine them into an overall equation.

For CaCO₃ → CaO + CO₂, ΔH = +178 kJ mol⁻¹ and ΔS = +161 J K⁻¹ mol⁻¹. Calculate the minimum temperature at which the reaction is feasible.

Explain why the entropy change for this reaction is positive.

Initial rates for A + B → products (data are illustrative, written for this paper):

Exp	[A] / mol dm⁻³	[B] / mol dm⁻³	Rate / mol dm⁻³ s⁻¹
1	0.10	0.10	2.0 × 10⁻⁴
2	0.20	0.10	8.0 × 10⁻⁴
3	0.10	0.20	4.0 × 10⁻⁴

Deduce the order with respect to A and B and write the rate equation.

Calculate the rate constant, k, with units.

A plot of ln k against 1/T has a gradient of −6000 K. Calculate the activation energy in kJ mol⁻¹.

N₂O₄(g) ⇌ 2NO₂(g). At equilibrium the total pressure is 200 kPa and the mole fraction of NO₂ is 0.40. Calculate Kp.

The forward reaction is endothermic. State and explain the effect of increasing temperature on Kp.

Calculate the EMF of a cell made from Zn²⁺/Zn (E° = −0.76 V) and Cu²⁺/Cu (E° = +0.34 V), and identify the positive electrode.

Describe the standard hydrogen electrode.

Give one advantage and one disadvantage of hydrogen fuel cells compared with rechargeable lithium-ion cells.

Calculate the pH of 0.0500 mol dm⁻³ hydrochloric acid.

Calculate the pH of 0.100 mol dm⁻³ ethanoic acid. (Ka = 1.74 × 10⁻⁵ mol dm⁻³)

Calculate the pH of a buffer containing 0.100 mol dm⁻³ ethanoic acid and 0.150 mol dm⁻³ sodium ethanoate. (pKa = 4.76)

At 50 °C, Kw = 5.47 × 10⁻¹⁴ mol² dm⁻⁶. Calculate the pH of pure water at 50 °C and explain why the water is still neutral.

Explain the trend in atomic radius across Period 3.

Explain why magnesium hydroxide is used to treat indigestion. Include an equation.

Explain why sodium bromide reacts with concentrated sulfuric acid to give bromine, but sodium chloride does not give chlorine.

Write an equation for the reaction of chlorine with water and give one benefit and one risk of chlorinating drinking water.

Write equations for the reactions of sodium oxide and sulfur trioxide with water.

State what is meant by aluminium oxide being amphoteric.

Explain why transition metal complexes are coloured.

Describe how you would use aqueous sodium hydroxide and aqueous ammonia to distinguish between solutions containing Cu²⁺, Fe³⁺ and Al³⁺ ions. Include observations and equations.

Explain how iron acts as a heterogeneous catalyst in the Haber process.