A-Level CIE Chemistry 1.7 Kinetics: Benzene(disodium chloride, C6H5N

Question

Benzene(disodium chloride, C6H5NaCl), is readily hydrolyzed at temperatures above 50°C, forming phenol, nitrogen gas and hydrochloric acid.

C6H5NaCl + H2O → C6H5OH + N2(g) + HCl(g)

The progress of the reaction can be monitored by measuring the volume of gas produced over time.
It has been established that V, the volume of the gas produced, is proportional to the amount of benzene(diasodium chloride) that has been hydrolyzed. The initial volume of gas produced, V0, is proportional to the initial concentration of benzene(diasodium chloride).

The order of reaction can be determined from these results.

(a)(i) The experimentally determined volumes of gas produced during the hydrolysis of benzene(diasodium chloride) at 50 °C is given in the table below:

| V0 (cm³) | Volume, V (cm³) |
|-----------|-------------------|
| 600       | 252               |
| 500       | 220               |
| 400       | 190               |
| 300       | 165               |
| 200       | 142               |
| 100       | 123               |
| 92        | 92                |
| 68        | 68                |
| 59        | 59                |

(ii) Plot a graph to show how V / V0 - V varies with time.

Use a cross (×) to plot each data point. Draw the curve of best fit.

(iii) Do you think the results obtained in (i) are reliable? Explain your answer.

(iv) Use the graph to determine the half-life, t1/2 of this reaction.

State the co-ordinates of both points you used in your calculation.

co-ordinates 1: (  )
co-ordinates 2: (  )

(v) A student set up an experiment to determine the order of the reaction in detail. Part of the experimental setup is shown below:

[Diagram not available in text format]

(ii) Complete the diagram above to show the experimental setup the student could have used to collect and measure the volume of gas evolved by the reaction.

(iii) At a lower temperature of 15 °C, the measurements made would be less accurate than measurements made at room temperature.

State why the measurements made at a higher temperature are less accurate.

State the effect this will have on the values of V0 and V.

(c) The graph below shows the results obtained from another benzene(diasodium chloride) hydrolysis reaction performed at different temperatures.

(i) The plot at time = 450s is considered to be anomalous.

Suggest what caused the anomaly.

(ii) The rate of reaction at different times can be calculated by drawing tangents to the best-fit line. The gradient of the tangent is equal to the rate of reaction; in this case, the slope of the tangent at 200s and write this value in the table below.

Draw a tangent to this one at time = 200s... (continued)

Benzene(disodium chloride, C6H5NaCl), is readily hydrolyzed at temperatures above 50°C, forming phenol, nitrogen gas and hydrochloric acid - CIE - A-Level Chemistry - Question 2 - 2016 - Paper 1

Worked Solution & Example Answer:Benzene(disodium chloride, C6H5NaCl), is readily hydrolyzed at temperatures above 50°C, forming phenol, nitrogen gas and hydrochloric acid - CIE - A-Level Chemistry - Question 2 - 2016 - Paper 1

i) The experimentally determined volumes of gas produced

ii) Plot a graph to show how V / V0 - V varies with time

iii) Do you think the results obtained in (i) are reliable? Explain your answer.

iv) Use the graph to determine the half-life, t1/2 of this reaction.

v) Complete the diagram above

vi) State why the measurements made at a higher temperature are less accurate

vii) State the effect this will have on the values of V0 and V

c) i) The plot at time = 450s is considered to be anomalous.

ii) Calculate the rate of reaction at 200s

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