7405-2-QP-Chemistry-A-13Oct20-AM ALL 100% C0RRECT AID GRADE A+

This question is about rates of reaction. Phosphinate ions (H2PO –) react with hydroxide ions to produce hydrogen gas as 2 shown. – − 2– H2PO2 + OH →HPO3 + H2 A student completed an 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 Units3 Do not write outside the *03* IB/M/Jun20/7405/2 . 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 – –3 Initial [H2PO2 ] / mol dm 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). box Deduce the order of the reaction with respect to phosphinate. [2 marks] Relationship Order Question 1 continues on the next page Turn over ► 0 14 Do not write outside the *04* IB/M/Jun20/7405/2 3 4 . Complete the diagram in Figure 2 to show how the hydrogen gas could be collected and measured in the experiments in Questions 01.1 and 01.2. box [1 mark] Figure 2 The rate equation for a different reaction is rate = k [L] [M]2 . Deduce the overall effect on the rate of reaction when the concentrations of both L and M are halved. [1 mark] 0 1 0 15 Do not write outside the box *05* IB/M/Jun20/7405/2 6 0 1 . 5 The rate of reaction is 0.0250 mol dm–3 s–1 when the concentration of L is 0.0155 mol dm–3 Calculate the concentration of M if the rate constant is 21.3 mol–2 dm6 s–1 [3 marks] Concentration of M mol dm–3 . Define the term overall order of reaction. [1 mark] Turn over for the next question Turn over ► 0 1 116 Do not write outside the box *06* IB/M/Jun20/7405/2 1 2 3 0 2 Prilocaine is used as an anaesthetic in dentistry. Figure 3 shows the structure of prilocaine. Figure 3 . Draw a circle around any chiral centre(s) in Figure 3. [1 mark] . Identify the functional group(s) in the prilocaine molecule. [1 mark] Tick () the box(es) corresponding to the functional group(s). Amide Amine Ester Ketone . Prilocaine is completely hydrolysed in the human body to give a mixture of products. Draw the structures of the two organic products formed in the complete hydrolysis of prilocaine in acidic conditions. [3 marks] 0 2 0 2 0 27 Do not write outside the IB/M/Jun20/7405/2 . 4 Figure 4 shows optical isomers F and G. Figure 4 Isomer F is the active compound in the medicine ibuprofen. In the manufacture of ibuprofen both isomers F and G are formed. An enzyme is then used to bind to isomer G and catalyse its hydrolysis. After the products of hydrolysis of G are removed, a pure sample of isomer F is collected. Explain how a structural feature of this enzyme enables it to catalyse the hydrolysis of isomer G but not the hydrolysis of isomer F. box [2 marks] Turn over for the next question *07* Turn over ► 0 2