1.325 g of anhydrous Na₂CO₃ (Mᵣ 106.0) was dissolved and made up to 250.0 cm³. 25.0 cm³ portions were titrated with hydrochloric acid; the mean titre was 24.10 cm³. Calculate the concentration of the acid.
1(b)3 marks
The balance reads to ±0.001 g (mass by difference), the pipette is ±0.06 cm³ and each burette reading is ±0.05 cm³. Calculate the overall percentage uncertainty.
1(c)2 marks
Explain why the burette should be rinsed with the acid and not with water before filling.
2(a)3 marks
Marble chips (in excess) reacted with 50.0 cm³ of hydrochloric acid. Figure 1 shows the volume of CO₂ collected. Use the graph to determine the initial rate of reaction.
Figure 1
2(b)3 marks
Explain the shape of the curve.
Figure 1
2(c)3 marks
The final volume of CO₂ was 80 cm³ at RTP. Calculate the concentration of the acid.
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
Figure 1
3(a)4 marks
Concentrated HCl is added to aqueous copper(II) sulfate. Write an equation and describe the changes in colour, shape and coordination number.
3(b)5 marks
4.90 g of ammonium iron(II) sulfate, (NH₄)₂Fe(SO₄)₂·xH₂O, was dissolved and made up to 250 cm³. 25.0 cm³ portions needed 12.50 cm³ of 0.0200 mol dm⁻³ KMnO₄.
MnO₄⁻ + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O
Determine x.
4(a)*6 marks
Three unlabelled bottles contain butan-1-ol, butan-2-ol and 2-methylpropan-2-ol. Plan an experiment, using acidified potassium dichromate(VI) and other reagents, to identify each alcohol.
4(b)4 marks
Explain which of the three alcohols shows optical isomerism, and predict the number of peaks in the ¹³C NMR spectrum of each alcohol.
5(a)4 marks
50.0 cm³ of 1.00 mol dm⁻³ HCl was mixed with 50.0 cm³ of 1.00 mol dm⁻³ NaOH. The temperature rose by 6.8 °C. Calculate the enthalpy change of neutralisation.
5(b)2 marks
Explain why ethanoic acid gives a less exothermic value.
5(c)4 marks
For ZnO(s) + C(s) → Zn(s) + CO(g), ΔH = +238 kJ mol⁻¹ and ΔS = +285 J K⁻¹ mol⁻¹. Calculate the minimum temperature for the reaction to be feasible and explain why ΔS is positive.
6(a)2 marks
Figure 2 shows the pH curve when 25.0 cm³ of a weak acid HA was titrated with 0.100 mol dm⁻³ NaOH. Use the curve to find pKa and Ka.
Figure 2
6(b)2 marks
Explain whether phenolphthalein (pH 8.2–10.0) or methyl orange (pH 3.1–4.4) should be used for this titration.
Figure 2
6(c)3 marks
Calculate the pH after 40.0 cm³ of NaOH has been added.
Figure 2
7*6 marks
Explain the trend in boiling points of the halogens from fluorine to iodine, and the trend in boiling points of the hydrogen halides from HF to HI.
8(a)4 marks
N₂(g) + 3H₂(g) ⇌ 2NH₃(g), ΔH = −93 kJ mol⁻¹. Explain why a temperature of about 450 °C and an iron catalyst are used.
8(b)3 marks
Use the bond enthalpies N≡N 945, H–H 436 and N–H 391 kJ mol⁻¹ to calculate ΔH for this reaction.
8(c)3 marks
Give three ways in which the Haber process is designed to be sustainable.
Finished?
Answer every question to finish (20 left), or finish when the time’s up.
Score 0 / 70 · 0 of 20 marked
This paper is written by Plasmo in the style of the OCR A-Level Chemistry exam. It is not a past paper and is not produced or endorsed by the exam board.