11.4. The reactions of chlorine
A subsection of Chemistry, 9701, through 11. Group 17
Listing 10 of 290 questions
The rate of reaction between 2-chloro-2-methylpropane, (CH3)3CCl, and methanol is investigated. When a large excess of methanol is used, the overall reaction is first order. (CH3)3CCl + CH3OH → (CH3)3COCH3 + HCl Fig.3.1 shows the results obtained. 0.0200 0.0175 0.0150 0.0125 0.0100 0.0075 0.0050 0.0025 0.0000 time / s [(CH3)3CCl ] / mol dm–3 Use the graph to determine the rate of reaction at 40 s. Show all your working.  rate = mol dm–3 s–1 Use the graph to show that the overall reaction is first order. Explain your answer. In a different reaction, which is also a first order reaction, 75% of the reactant is consumed in 320 s. Calculate the rate constant, k, for this reaction. State the units for k.  k = units = Define standard electrode potential, E o. A salt bridge is used in an electrochemical cell. State the function of the salt bridge. Explain your answer. Complete the diagram of the apparatus that can be used to measure the E o of the Cr2O7 2–, H+/Cr3+electrode against the standard hydrogen electrode. Your diagram should be fully labelled to identify all apparatus, substances and conditions. salt bridge  The E o of the Cr2O7 2–, H+/Cr3+electrode is +1.33 V. Label the negative electrode and the direction of electron flow in the external circuit when the current flows in your diagram in . Table3.1 lists relevant electrode potentials for some electrode reactions for use in and . Table 3.1 electrode reaction E o / V Cr2O7 2– + 14H+ + 6e– 2Cr3+ + 7H2O +1.33 CH3CHO + 2H+ + 2e– CH3CH2OH –0.61 CH3COOH + 2H+ + 2e– CH3CHO + H2O –0.94 O2 + 4H+ + 4e– 2H2O +1.23 Ethanal is oxidised to ethanoic acid in the presence of Cr2O7 2– ions. Construct the ionic equation for the oxidation of ethanal to ethanoic acid using dichromate(in acid conditions. Calculate the for this reaction. ionic equation  = V  In an ethanol-oxygen fuel cell, CH3CH2OHand O2are in contact with two inert electrodes immersed in an acidic solution. The cell reaction for the oxidation of ethanol by oxygen is shown. 2CH3CH2OH + O2 → 2CH3COOH + 2H2O = +2.01 V Calculate ∆G o, in kJ mol–1, for the oxidation of ethanol by oxygen. ∆G o = kJ mol–1 
9701_s22_qp_41
THEORY
2022
Paper 4, Variant 1
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The rate of reaction between 2-chloro-2-methylpropane, (CH3)3CCl, and methanol is investigated. When a large excess of methanol is used, the overall reaction is first order. (CH3)3CCl + CH3OH → (CH3)3COCH3 + HCl Fig.3.1 shows the results obtained. 0.0200 0.0175 0.0150 0.0125 0.0100 0.0075 0.0050 0.0025 0.0000 time / s [(CH3)3CCl ] / mol dm–3 Use the graph to determine the rate of reaction at 40 s. Show all your working.  rate = mol dm–3 s–1 Use the graph to show that the overall reaction is first order. Explain your answer. In a different reaction, which is also a first order reaction, 75% of the reactant is consumed in 320 s. Calculate the rate constant, k, for this reaction. State the units for k.  k = units = Define standard electrode potential, E o. A salt bridge is used in an electrochemical cell. State the function of the salt bridge. Explain your answer. Complete the diagram of the apparatus that can be used to measure the E o of the Cr2O7 2–, H+/Cr3+electrode against the standard hydrogen electrode. Your diagram should be fully labelled to identify all apparatus, substances and conditions. salt bridge  The E o of the Cr2O7 2–, H+/Cr3+electrode is +1.33 V. Label the negative electrode and the direction of electron flow in the external circuit when the current flows in your diagram in . Table3.1 lists relevant electrode potentials for some electrode reactions for use in and . Table 3.1 electrode reaction E o / V Cr2O7 2– + 14H+ + 6e– 2Cr3+ + 7H2O +1.33 CH3CHO + 2H+ + 2e– CH3CH2OH –0.61 CH3COOH + 2H+ + 2e– CH3CHO + H2O –0.94 O2 + 4H+ + 4e– 2H2O +1.23 Ethanal is oxidised to ethanoic acid in the presence of Cr2O7 2– ions. Construct the ionic equation for the oxidation of ethanal to ethanoic acid using dichromate(in acid conditions. Calculate the for this reaction. ionic equation  = V  In an ethanol-oxygen fuel cell, CH3CH2OHand O2are in contact with two inert electrodes immersed in an acidic solution. The cell reaction for the oxidation of ethanol by oxygen is shown. 2CH3CH2OH + O2 → 2CH3COOH + 2H2O = +2.01 V Calculate ∆G o, in kJ mol–1, for the oxidation of ethanol by oxygen. ∆G o = kJ mol–1 
9701_s22_qp_43
THEORY
2022
Paper 4, Variant 3
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