Acetic acid and ethanol react to form ethyl acetate and water, like this: HCH_3
ID: 529824 • Letter: A
Question
Acetic acid and ethanol react to form ethyl acetate and water, like this: HCH_3 CO_2(aq) + C_2 H_5 OH(aq) rightarrow C_2 H_5 CO_2 CH_3(aq) + H_2 O(I) Imagine 185. mmol of HCH_3 CO_2 are removed from a flask containing a mixture of HCH_3 CO_2, C_2 H_5 OH, C_2 H_5 CO_2 CH_3 and H_2 O at equilibrium, and then answer the following questions. What is the rate of the forward reaction before any HCH_3 CO_2 has been removed from the flask? Zero. Greater than zero, but less than the rate of the reverse reaction. Greater than zero, and equal to the rate of the reverse reaction. Greater than zero, and greater than the rate of the reverse reaction. What is the rate of the forward reaction just after the HCH_3 CO_2 has been removed from the flask? Zero. Greater than zero, but less than the rate of the reverse reaction. Greater than zero, and equal to the rate of the reverse reaction. Greater than zero, and greater than the rate of the reverse reaction. What is the rate of the forward reaction when the system has again reached equilibrium? Zero. Greater than zero, but less than the rate of the reverse reaction. Greater than zero, and equal to the rate of the reverse reaction. Greater than zero, and greater than the rate of the reverse reaction. How much less HCH_3 CO_2 is in the flask when the system has again reached equilibrium? None. Some, but less than 185. mmol. 185. mmol. More than 185. mmol.Explanation / Answer
1) At equilibrium the rate of forward reaction will be equal to the reverse reation. Since the system was at equilibrium before any HCH3CO2 was removed the correct option will be C) It will be greater than zero, and equal to the rate of the reverse reaction.
2) Just after the HCH3CO2 has been removed the equilibrium will be disturbed and as per Lee Chatelier's principle the reaction will shift to the direction where the effect of change can be negated. Therefore, the reaction will be in backward direction so that HCH3CO2 will be formed to negate the effect of its removal. Therefore, the correct option will be B) Forward reaction will be greater than zero, but less than the rate of the reverse reaction.
3) At equilibrium the rate of forward reaction will be equal to the reverse reation. Since the system again attained equilibrium the rate of forward reaction will be equal to the rate of the reverse reaction. Correct option is C.
4) The concentration of HCH3CO2 will increase as the reverse reaction will be more as per the Lee Chateliers principle. At equilibrium it will recover the concentation that has been removed however the recovered amount will be less that the amount removed that is 185 mmol. Correct option is B) Some, but less than 185 mmol.