A-level CHEMISTRY Paper 2 Organic and Physical Chemistry Monday 8 June 2021

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This question is about rates of reaction. Phosphinate ions (H2PO2 – ) react with hydroxide ions to produce hydrogen gas as shown. H2PO2 – + OH− → HPO3 2– + H2 A student completed a... n experiment to determine the initial rate of this reaction. The student used a solution containing phosphinate ions and measured the volume of hydrogen gas collected every 20 seconds at a constant temperature. Figure 1 shows a graph of the student’s results. Figure 1 0 1 . 1 Use the graph in Figure 1 to determine the initial rate of reaction for this experiment. State its units. Show your working on the graph. [3 marks] Rate Units 3 *03* Turn over ► IB/M/Jun20/7405/2 Do not write outside the 0 1 box . 2 Another student reacted different initial concentrations of phosphinate ions with an excess of hydroxide ions. The student measured the time (t) taken to collect 15 cm3 of hydrogen gas. Each experiment was carried out at the same temperature. Table 1 shows the results. Table 1 Initial [H2PO2 – ] / mol dm–3 t / s 0.25 64 0.35 32 0.50 16 1.00 4 State the relationship between the initial concentration of phosphinate and time (t). Deduce the order of the reaction with respect to phosphinate. [Show More]

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