Paper 1: Inorganic and Physical Chemistry

A sample of gallium contains 60.1% ⁶⁹Ga and 39.9% ⁷¹Ga. Calculate the relative atomic mass of gallium to 1 decimal place.

Give the electron configuration of an Fe³⁺ ion.

Explain why the first ionisation energy of sulfur is lower than that of phosphorus.

In a time-of-flight mass spectrometer, ⁷¹Ga⁺ ions are accelerated to a kinetic energy of 1.00 × 10⁻¹⁶ J and travel along a 1.50 m flight tube. Calculate the time of flight. KE = 1/2 mv².

Name the shape of XeF₄ and give the bond angle.

Explain why ice is less dense than liquid water.

0.640 g of a gas occupies 250 cm³ at 100 kPa and 300 K. Calculate its relative molecular mass and suggest its identity.

In a reaction the theoretical yield was 4.80 g and the actual yield 3.36 g. Calculate the percentage yield and give one reason why it is less than 100%.

Use the data to calculate the enthalpy of lattice formation of sodium chloride.

Enthalpy change	ΔH / kJ mol⁻¹
Formation of NaCl(s)	−411
Atomisation of Na	+107
First ionisation energy of Na	+496
Atomisation of chlorine (½Cl₂ → Cl)	+122
First electron affinity of Cl	−349

The value calculated from the perfect ionic model is less exothermic than the Born–Haber value for silver chloride, but almost the same for sodium chloride. Explain why.

For the decomposition of a carbonate, ΔH = +117 kJ mol⁻¹ and ΔS = +175 J K⁻¹ mol⁻¹. Calculate the minimum temperature at which the reaction is feasible.

Explain why the entropy change for this decomposition is positive.

1.00 mol of H₂ and 1.00 mol of I₂ were heated in a 2.00 dm³ flask. At equilibrium, 1.56 mol of HI was present. H₂(g) + I₂(g) ⇌ 2HI(g) Calculate Kc.

For N₂O₄(g) ⇌ 2NO₂(g), at equilibrium the total pressure is 200 kPa and the mole fraction of NO₂ is 0.400. Calculate Kp and give its units.

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

State the effect of a catalyst on Kp and on the time taken to reach equilibrium.

The initial rate of the reaction between A and B was measured.

Experiment	[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 rate equation and calculate the rate constant, with units.

The rate constant is 0.20 at 300 K and 0.80 at 320 K. Use ln k = ln A - E_a/RT to calculate the activation energy in kJ mol⁻¹.

Explain why the rate equation suggests the rate-determining step involves two particles of A and one of B, and suggest why a single-step mechanism is unlikely.

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.

Write the conventional representation of this cell.

Write the half-equations at each electrode in an alkaline hydrogen–oxygen fuel cell and give one disadvantage of fuel cells.

Explain why the salt bridge is made using potassium nitrate solution rather than potassium chloride.

Explain why lithium-ion cells can be recharged but zinc–carbon cells cannot.

Calculate the pH of 0.025 mol dm⁻³ barium hydroxide solution at 298 K (Kw = 1.00 × 10⁻¹⁴ mol² dm⁻⁶).

A buffer contains 0.10 mol of ethanoic acid and 0.050 mol of sodium ethanoate in 1.00 dm³. Ka = 1.74 × 10⁻⁵ mol dm⁻³. Calculate the pH.

0.010 mol of HCl is added to this buffer. Calculate the new pH.

Figure 1 shows the pH curve for ethanoic acid titrated with sodium hydroxide. Explain why phenolphthalein (range 8.3–10.0) is a suitable indicator but methyl orange (range 3.1–4.4) is not.

At 50 °C, Kw = 5.48 × 10⁻¹⁴ mol² dm⁻⁶. Calculate the pH of pure water at 50 °C and explain whether it is acidic.

Describe the difference in how magnesium and calcium react with water.

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

Write an equation for the reaction of chlorine with water, and use oxidation states to explain why it is a disproportionation reaction.

Describe a test for sulfate ions and explain why the solution is acidified first.

Write an equation for the reaction of sodium oxide with water and give the approximate pH of the solution.

Explain why the melting point of MgO is much higher than that of P₄O₁₀.

Concentrated hydrochloric acid is added to aqueous copper(II) sulfate. Write an equation, give the colour change and the change in shape of the complex.

Explain, in terms of entropy, why [Cu(EDTA)]²⁻ forms readily from [Cu(H₂O)₆]²⁺.

6.30 g of hydrated iron(II) sulfate, FeSO₄·xH₂O, was dissolved and made up to 250 cm³. A 25.0 cm³ portion required 22.40 cm³ of 0.0200 mol dm⁻³ KMnO₄ in acidic solution. MnO₄⁻ + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 4H₂O + 5Fe³⁺ Calculate the value of x.