7.1. Chemical equilibria: reversible reactions, dynamic equilibrium
A subsection of Chemistry, 9701, through 7. Equilibria
Listing 10 of 211 questions
One method of producing hydrogen from natural gas is the reaction between hydrogen sulfide and methane. 2H2S+ CH4CS2+ 4H2Write the expression for Kp for this reaction, and state its units. Kp = units The initial partial pressures of the two gases in a mixture at 1000 K are recorded. H2S200 atm CH4100 atm The mixture is left to reach equilibrium. It is found that the equilibrium partial pressure of CS2is 2 atm and that of the remaining CH4is 98 atm. Calculate the equilibrium partial pressures of H2Sand H2. p(H2S) = atm p(H2) = atm Calculate the value of Kp at this temperature. Kp = Predict the sign of ∆S o for this reaction. Explain your answer. 2H2S+ CH4CS2+ 4H2∆H o = +241 kJ mol–1 The free energy change, ∆G o, for this reaction at 1000 K is +51 kJ mol–1. Calculate the value of ∆S o for this reaction, stating its units. ∆S o = units How would the value of ∆G o, and hence the spontaneity of this reaction change as the temperature increases? Explain your answer.
9701_s16_qp_43
THEORY
2016
Paper 4, Variant 3
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N2reacts with H2in the Haber process, as shown in reaction 1. reaction 1 N2+ 3H22NH3ΔH = –x kJ mol–1 Table 2.1 shows the different conditions used to produce three equilibrium mixtures, A, B and C. Table 2.1 A B C initial molar ratio of N2 : H2 added 1 : 3 1 : 3 1 : 3 temperature / °C pressure / atm iron present in mixture no yes no percentage yield of NH3at equilibrium x y Describe and explain the change, if any, to the percentage yield of NH3produced in B compared to A. Describe and explain the change, if any, to the percentage yield of NH3produced in C compared to A. Describe and explain the change to the rate of the forward reaction that occurs to establish the equilibrium in C compared to A. You do not need to refer to the Boltzmann distribution in your answer. Write an expression for the equilibrium constant, Kp, for reaction 1. State the units. Kp = units Equilibrium mixture D is made when 1.0 mol of N2and 3.0 mol of H2are added to a sealed container at 750 °C and 1000 atm and left to reach equilibrium. This mixture contains 1.16 mol of NH3. Calculate the mole fraction of NH3in D. mole fraction of NH3= The mole fraction of N2is 0.625 in a new equilibrium mixture, E. Calculate the partial pressure of N2in E when the total pressure is 1000 atm. partial pressure of N2= atm When oxides of nitrogen escape into the atmosphere they may be involved in: • formation of acid rain from sulfur dioxide • formation of photochemical smog. Identify the role of NO and NO2 in the formation of H2SO4 from SO2 in the atmosphere to produce acid rain. Use relevant equations to support your answer. Outline how NO and NO2 may contribute to the formation of photochemical smog.
9701_s24_qp_23
THEORY
2024
Paper 2, Variant 3
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The diagram shows a gas syringe with a free-moving piston. The syringe contains gaseous hydrogen, gaseous iodine and gaseous hydrogen iodide at equilibrium. gaseous hydrogen, gaseous iodine and gaseous hydrogen iodide sealed end piston H2+ I2⇋2HIThree changes are listed. increasing the total pressure by adding an inert gas and keeping the volume constant increasing the pressure by adding more gaseous hydrogen iodide and keeping the volume constant decreasing the volume by pushing the piston to the left Which changes will result in an equilibrium position at which the rate of the forward reaction has increased?
9701_w23_qp_12
MCQ
2023
Paper 1, Variant 2
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Questions Discovered
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