8.1. Rate of reaction
A subsection of Chemistry, 9701, through 8. Reaction kinetics
Listing 10 of 86 questions
Ethyl ethanoate is hydrolysed slowly by water in the following acid-catalysed reaction. H+ CH3CO2CH2CH3 + H2O CH3CO2H + CH3CH2OH The concentration of ethyl ethanoate was determined at regular time intervals as the reaction progressed. Two separate experiments were carried out, with different HCl concentrations. The following graph shows the results of an experiment using = 0.1 mol dm–3. 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 time / min / mol dm–3 When the experiment was carried out using = 0.2 mol dm–3, the following results were obtained. time / min / mol dm–3 0.200 0.160 0.115 0.067 0.038 0.022 0.013 Plot these data on the axes above, and draw a line of best fi t. Use one of the graphs to show that the reaction is fi rst order with respect to CH3CO2CH2CH3. Show all your working, and show clearly any construction lines you draw on the graphs. Use the graphs to calculate the order of reaction with respect to HCl. Show all your working, and show clearly any construction lines you draw on the graphs. Write the rate equation for this reaction, and calculate the value of the rate constant. rate = Why is it not possible to determine the order of reaction with respect to water in this experiment? Although decreases during each experiment, remains the same as its initial value. Why is this?
9701_s13_qp_41
THEORY
2013
Paper 4, Variant 1
View
Ethyl ethanoate is hydrolysed slowly by water in the following acid-catalysed reaction. H+ CH3CO2CH2CH3 + H2O CH3CO2H + CH3CH2OH The concentration of ethyl ethanoate was determined at regular time intervals as the reaction progressed. Two separate experiments were carried out, with different HCl concentrations. The following graph shows the results of an experiment using = 0.1 mol dm–3. 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 time / min / mol dm–3 When the experiment was carried out using = 0.2 mol dm–3, the following results were obtained. time / min / mol dm–3 0.200 0.160 0.115 0.067 0.038 0.022 0.013 Plot these data on the axes above, and draw a line of best fi t. Use one of the graphs to show that the reaction is fi rst order with respect to CH3CO2CH2CH3. Show all your working, and show clearly any construction lines you draw on the graphs. Use the graphs to calculate the order of reaction with respect to HCl. Show all your working, and show clearly any construction lines you draw on the graphs. Write the rate equation for this reaction, and calculate the value of the rate constant. rate = Why is it not possible to determine the order of reaction with respect to water in this experiment? Although decreases during each experiment, remains the same as its initial value. Why is this?
9701_s13_qp_43
THEORY
2013
Paper 4, Variant 3
View
The reaction between 1-chloro-1-phenylethane and hydroxide ions to produce 1-phenylethanol is: C6H5CHCl CH3 + OH– C6H5CH(OH)CH3 + Cl – 1-chloro-1-phenylethane 1-phenylethanol The rate of this reaction can be studied by measuring the amount of hydroxide ions that remain in solution at a given time. The reaction can effectively be stopped if the solution is diluted with an ice-cold solvent. Describe a suitable method for studying the rate of this reaction at a temperature of 40 °C, given the following. ● a solution of 0.10 mol dm–3 1-chloro-1-phenylethane, labelled A ● a solution of 0.10 mol dm–3 sodium hydroxide, labelled B ● 0.10 mol dm–3 HCl ● volumetric glassware ● ice-cold solvent ● stopclock ● access to standard laboratory equipment and chemicals The rate of this reaction was measured at different initial concentrations of the two reagents. The table shows the results obtained. experiment [C6H5CHCl CH3] / mol dm–3 [OH–] / mol dm–3 relative rate 0.05 0.10 0.5 0.10 0.20 1.0 0.15 0.10 1.5 0.20 0.15 to be calculated Deduce the order of reaction with respect to each of [C6H5CHCl CH3] and [OH–]. Explain your reasoning. order with respect to [C6H5CHCl CH3] order with respect to [OH–]  Write the rate equation for this reaction, stating the units of the rate constant, k. rate = mol dm–3 s–1 units of k = Calculate the relative rate for experiment 4. relative rate for experiment 4 = Use your answers in to help you to draw the mechanism for the reaction of 1-chloro-1-phenylethane with hydroxide ions, including the following. ● all relevant lone pairs and dipoles ● curly arrows to show the movement of electron pairs ● the structures of any transition state or intermediate This reaction was carried out using a single optical isomer of 1-chloro-1-phenylethane. Use your mechanism in to predict whether the product will be a single optical isomer or a mixture of two optical isomers. Explain your answer. The proton NMR spectrum of a sample of 1-phenylethanol shows four peaks: a multiplet for the C6H5 protons and three other peaks as shown in the table. When the sample is shaken with D2O and the proton NMR spectrum recorded, fewer peaks are seen. Complete the table for the proton NMR spectrum of 1-phenylethanol, C6H5CH(OH)CH3. Use of the Data Booklet might be helpful. δ / ppm number of 1H atoms responsible for the peak group responsible for the peak splitting pattern result on shaking with D2O 1.4 2.7 4.0 7.2-7.4 C6H5 multiplet peak remains
9701_s17_qp_41
THEORY
2017
Paper 4, Variant 1
View
The reaction between 1-chloro-1-phenylethane and hydroxide ions to produce 1-phenylethanol is: C6H5CHCl CH3 + OH– C6H5CH(OH)CH3 + Cl – 1-chloro-1-phenylethane 1-phenylethanol The rate of this reaction can be studied by measuring the amount of hydroxide ions that remain in solution at a given time. The reaction can effectively be stopped if the solution is diluted with an ice-cold solvent. Describe a suitable method for studying the rate of this reaction at a temperature of 40 °C, given the following. ● a solution of 0.10 mol dm–3 1-chloro-1-phenylethane, labelled A ● a solution of 0.10 mol dm–3 sodium hydroxide, labelled B ● 0.10 mol dm–3 HCl ● volumetric glassware ● ice-cold solvent ● stopclock ● access to standard laboratory equipment and chemicals The rate of this reaction was measured at different initial concentrations of the two reagents. The table shows the results obtained. experiment [C6H5CHCl CH3] / mol dm–3 [OH–] / mol dm–3 relative rate 0.05 0.10 0.5 0.10 0.20 1.0 0.15 0.10 1.5 0.20 0.15 to be calculated Deduce the order of reaction with respect to each of [C6H5CHCl CH3] and [OH–]. Explain your reasoning. order with respect to [C6H5CHCl CH3] order with respect to [OH–]  Write the rate equation for this reaction, stating the units of the rate constant, k. rate = mol dm–3 s–1 units of k = Calculate the relative rate for experiment 4. relative rate for experiment 4 = Use your answers in to help you to draw the mechanism for the reaction of 1-chloro-1-phenylethane with hydroxide ions, including the following. ● all relevant lone pairs and dipoles ● curly arrows to show the movement of electron pairs ● the structures of any transition state or intermediate This reaction was carried out using a single optical isomer of 1-chloro-1-phenylethane. Use your mechanism in to predict whether the product will be a single optical isomer or a mixture of two optical isomers. Explain your answer. The proton NMR spectrum of a sample of 1-phenylethanol shows four peaks: a multiplet for the C6H5 protons and three other peaks as shown in the table. When the sample is shaken with D2O and the proton NMR spectrum recorded, fewer peaks are seen. Complete the table for the proton NMR spectrum of 1-phenylethanol, C6H5CH(OH)CH3. Use of the Data Booklet might be helpful. δ / ppm number of 1H atoms responsible for the peak group responsible for the peak splitting pattern result on shaking with D2O 1.4 2.7 4.0 7.2-7.4 C6H5 multiplet peak remains
9701_s17_qp_43
THEORY
2017
Paper 4, Variant 3
View
Questions Discovered
86