Chemistry SL Paper 1B, May 2025, TZ2

Before use, the EDTA solution was standardized against a standard solution of $\ce{Cu^2+}$ ions. An accurately weighed piece of pure copper wire was dissolved in the minimum volume of concentrated nitric acid and the mixture was warmed gently until no more…

Anhydrous copper(II) chloride, $\ce{CuCl2}$, takes up water vapour from the air, so it cannot be weighed out accurately to make a standard solution. Suggest a laboratory procedure that would remove all of the absorbed water from a sample of solid $\ce{CuCl2}$…

Portions of the rinse water were then titrated with the standardized EDTA solution in the presence of murexide as indicator. The burette readings are given in the table. Trial 1 Trial 2 Trial 3 Trial 4 Final burette reading / $\mathrm{cm^3}$ (± 0.05…

For the AAS method, a series of standards of known concentration was prepared by diluting a stock solution of $\ce{Cu^2+}$ ions. The instrument was zeroed with deionized water and the absorbance of each standard was recorded. (i) Draw the line of best fit for…

(i) State the independent variable and the dependent variable of the investigation. (ii) Apart from the mass of leaves and the volume of water, suggest two other conditions that should be kept constant for the comparison between boiling times to be valid.

(i) State what the graph shows about the relationship between the boiling time and the amount of oxalate ions extracted. (ii) Comment on the range of boiling times and on the number of measurements made in the investigation.

The hypothesis being tested was that a longer boiling time would extract more oxalate ions from the leaves. (i) Evaluate the hypothesis in the light of the results, giving a reason. (ii) Suggest one way in which the investigation could be changed so that it…

(i) Determine, using a suitable construction drawn on the graph, the initial rate at which $\ce{CO2(g)}$ is released, in $\mathrm{g\,s^{-1}}$, in the reaction with 1.20 $\mathrm{mol\,dm^{-3}}$ $\ce{HNO3(aq)}$. (ii) Determine the average rate of release of…

For the runs with 0.40 and 0.80 $\mathrm{mol\,dm^{-3}}$ $\ce{HNO3(aq)}$, suggest which reactant, $\ce{CaCO3(s)}$ or $\ce{HNO3(aq)}$, was the limiting reagent. Give a reason for your answer.