Chemistry HL Paper 1B, May 2025, TZ3

(i) Suggest, giving a reason for each, two different safety precautions that should be taken when carrying out either of these preparations. (ii) Deduce the coefficients needed to balance the following equation for the reaction of silver with concentrated…

The sealed vessel was left for the reaction to proceed. Suggest two properties of the system, other than its colour, that could be measured to follow the progress of the reaction over time, and predict how each would change as the forward reaction proceeds.

A sample of 0.0120 mol of $\ce{NO2}$ was placed in a sealed vessel of volume 1.00 $\mathrm{dm^3}$, which was kept at a constant temperature of 35 °C. (i) Suggest a simple way of keeping the vessel at a constant temperature in a school laboratory. (ii) The…

A sample of 0.0120 mol of $\ce{NO2}$ was sealed in a vessel of volume 1.00 $\mathrm{dm^3}$ and kept at 10.0 °C until equilibrium was established. At equilibrium, 0.00860 mol of $\ce{NO2}$ remained in the vessel. Using the expression below, determine $K$ 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…

Describe how a standard aqueous solution of potassium manganate(VII) can be prepared from the solid.

Describe the steps by which this standard solution is turned into a calibration curve for the colorimeter.

Explain how the calibration curve is then used to determine the concentration of $\ce{KMnO4}$ in a reaction mixture of unknown concentration.

(i) Suggest a reason for the slight change in colour observed after the night in the oven. (ii) Suggest how the students could make sure that dehydration in the crucible was complete. (iii) Suggest one way in which the students could reduce the effect of…

Each student used a different mass of the hydrated salt. The results of the whole class are shown below ($M_r$ of $\ce{H2O}$ = 18.02). Student Mass of $\ce{CuSO4 * XH2O}$ / g Mass of $\ce{CuSO4}$ / g Loss in mass / g Amount of $\ce{CuSO4}$ / mol Amount of…