Paper 2 Organic and Physical Chemistry

*JUN20 7405201 *

IB/M/Jun20/E1 1 7405/2

For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 9 TOTAL

Monday 8 June 2020 Afternoon Time allowed: 2 hours

Materials

For this paper you must have:

• the Periodic Table/Data Booklet, provided as an insert (enclosed) • a ruler with millimetre measurements • a scientific calculator, which you are expected to use where appropriate.

Instructions • Use black ink or black ball-point pen.• Fill in the boxes at the top of this page.• Answer all questions.• You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages.• If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s).• All working must be shown.• Do all rough work in this book. Cross through any work you do not want to be marked.

Information • The marks for questions are shown in brackets.• The maximum mark for this paper is 105.

Please write clearly in block capitals.Centre number

Candidate number

Surname

Forename(s)

Candidate signature

I declare this is my own work.A-level

CHEMISTRY

Paper 2 Organic and Physical Chemistry

2

*02* IB/M/Jun20/7405/2

Do not write outside the box Answer all questions in the spaces provided.

• 1

This question is about rates of reaction.

Phosphinate ions (H2PO2 –) react with hydroxide ions to produce hydrogen gas as shown.

H 2PO2

– + OH

−

→ HPO 3

2– + 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

• 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 box

• 1

. 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 cm 3 of hydrogen gas. Each experiment was carried out at the same temperature.Table 1 shows the results.

Table 1

Initial [H 2PO2 –] / 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.[2 marks]

Relationship

Order

Question 1 continues on the next page

4

*04* IB/M/Jun20/7405/2

Do not write outside the box

• 1

. 3 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.[1 mark]

Figure 2

The rate equation for a different reaction is

rate = k [L] [M] 2

• 1

. 4

Deduce the overall effect on the rate of reaction when the concentrations of both L and M are halved.[1 mark]