Zadania z chemii IB SL

(b) A variety of ions are dissolved in the water of the Salton Sea. The concentrations of the major ions are shown in the table below, based on two different sources (both scientific journals). Ion Concentration / $\mathrm{g\,dm^{-3}}$, based on Source 1…

(c) A simple set-up was used to compare the conductivity of water samples obtained from the Salton Sea at different depths. The following data were obtained: Depth water sample was obtained from / m ($\pm 0.05\ \mathrm{m}$) Electric current recorded by the…

(c) After 30 minutes, the student stopped heating the mixture and titrated a sample of the solution remaining in the flask with NaOH to determine the experimental yield of propanoic acid. Explain why the titrated sample will give an incorrect value for the…

The student's results are shown below. Each time was measured to ± 0.1 s. Concentration of $\ce{Na2S2O3}$ / $\mathrm{mol\,dm^{-3}}$ Time, trial 1 / s Time, trial 2 / s Time, trial 3 / s Time, trial 4 / s Time, trial 5 / s Average time / s 0.2000 ± 0.08 % 17.2…

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…

The amount of $\ce{NO2}$ prepared was checked by titration. The gas was first absorbed in water: $\ce{2NO2(g) + H2O(l) -> HNO3(aq) + HNO2(aq)}$ The resulting solution was made up to 200.0 $\mathrm{cm^3}$ in a volumetric flask, and 20.0 $\mathrm{cm^3}$ portions…

The student recorded the following masses. Sample Mass / g (± 0.01 g) Percentage by mass Mixture before separation 6.35 not applicable Iron after separation 2.58 Calcium carbonate after separation 1.71 Potassium chloride after separation 2.31 36.4 % Calculate…

The three percentages in 2b add up to more than 100 %. Suggest an error that would explain this result and how it could be reduced or eliminated.