From Paper 1: Periodic table, elements and physical chemistry
16(a)3 marks
25.0 cm³ of sodium carbonate solution needed 23.50 cm³ of 0.150 mol dm⁻³ hydrochloric acid for neutralisation.
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
Calculate the concentration of the sodium carbonate solution.
From Paper 1: Periodic table, elements and physical chemistry
24(a)5 marks
10.0 cm³ of bleach was diluted to 250 cm³. 25.0 cm³ of this was added to excess acidified KI. The iodine released needed 18.60 cm³ of 0.0500 mol dm⁻³ Na₂S₂O₃.
ClO⁻ + 2I⁻ + 2H⁺ → Cl⁻ + I₂ + H₂O
I₂ + 2S₂O₃²⁻ → 2I⁻ + S₄O₆²⁻
Calculate the concentration of ClO⁻ in the original bleach.
From Paper 2: Synthesis and analytical techniques
18*6 marks
Cyclohexene can be made by heating cyclohexanol with concentrated phosphoric acid. Describe how to prepare and purify a sample of cyclohexene.
From Paper 3: Unified chemistry
1(a)4 marks
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.
From Paper 3: Unified chemistry
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.
From Paper 3: Unified chemistry
1(c)2 marks
Explain why the burette should be rinsed with the acid and not with water before filling.
From Paper 3: Unified chemistry
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
From Paper 3: Unified chemistry
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.
From Paper 3: Unified chemistry
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.
Score 0 / 36 · 0 of 9 marked
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