HL Paper 3
Bromine and methanoic acid react in aqueous solution.
Br2 (aq) + HCOOH (aq) → 2Br− (aq) + 2H+ (aq) + CO2 (g)
The reaction was monitored by measuring the volume of carbon dioxide produced as time
progressed.
Determine from the graph the rate of reaction at 20 s, in cm3 s−1, showing your working.
Outline, with a reason, another property that could be monitored to measure the rate of this reaction.
Describe one systematic error associated with the use of the gas syringe, and how the error affects the calculated rate.
Identify one error associated with the use of an accurate stopwatch.
This question is about a mug made of a lead alloy.
The rate of lead dissolving in common beverages with various pH values was analysed.
Identify the experiment with the highest rate of lead dissolving.
Suggest why the relationship between time and lead concentration for Cola at 16 °C is not linear.
Examine, giving a reason, whether the rate of lead dissolving increases with acidity at 18 °C.
Lead(II) chloride, PbCl2, has very low solubility in water.
PbCl2 (s) Pb2+ (aq) + 2Cl− (aq)
Explain why the presence of chloride ions in beverages affects lead concentrations.
A mean daily lead intake of greater than 5.0 × 10−6 g per kg of body weight results in increased lead levels in the body.
Calculate the volume, in dm3, of tap water from experiment 8 which would exceed this daily lead intake for an 80.0 kg man.