Experimental chemistry

© UCLES 2025 5070/11/O/N/25 [Turn over 21 The Group I metals lithium, sodium and potassium show trends in their melting points and in their reactions with water. Which statement is correct going down the group from lithium to potassium? A Their melting points decrease and their reaction with water becomes less vigorous. B Their melting points decrease and their reaction with water becomes more vigorous. C Their melting points increase and their reaction with water becomes less vigorous. D Their melting points increase and their reaction with water becomes more vigorous. 10

5070/42/O/N/24 © UCLES 2024 [Turn over 1 A student does an experiment to make pure hydrated copper( II ) sulfate crystals, CuSO 4 •5H 2 O. (a) The student makes aqueous copper( II ) sulfate by reacting a dilute acid with excess copper( II ) oxide. Name the acid. ............................................................................................................................................. [1] (b) Fig. 1.1 shows the apparatus the student uses to crystallise the aqueous copper( II ) sulfate. aqueous copper( II ) sulfate water X beaker gauze Fig. 1.1 (i) Name apparatus X. ...........

5070/42/M/J/24 © UCLES 2024 2 A student investigates the temperature change when a solid completely dissolves in water. The student: • measures 25 cm 3 of distilled water and pours it into a beaker • uses a thermometer to measure the initial temperature of the water in the beaker • records this temperature in Table 2.1 at time 0 s • adds a sample of the solid to the beaker and starts a stop-watch • stirs the mixture and records the temperature and time at 60 s intervals for a total of 300 s. Some of the results are shown in Table 2.1. Table 2.1 time / s temperature / ° C 0 19.5 60 13.0 120 180

© UCLES 2023 5070/12/O/N/23 30 Which statement about water is correct? A Distillation is used to remove insoluble impurities from the domestic water supply. B Water containing impurities turns anhydrous copper( II ) sulfate blue. C Water containing impurities turns cobalt( II ) chloride paper blue. D Water containing impurities boils at 100  C. 11

38 Which statement is correct? A A filtrate is a substance that remains on the filter paper after filtration. B A saturated solution has the maximum amount of solvent dissolved in the solute. C A solution is a compound produced when a solute reacts with a solvent. D A substance that remains in the heated flask after distillation is called a residue.