Question
Chem 212 Fall 2012 Midterm Exam #2 Form EF Name 1-5) The system below is initially at equilibrium. Predict the equilibrium response to each of changes described below. (circle one answer for each -2pt each) 2 NaHSO:(s)Na2SO3 (s) + H2O (g) SO2 (g) AH+ I) H20 gas is added to the reaction vessel 1.1) The equilibrium will: shift left shift right no shift 1.2) The new equilibrium partial pressure of SO2 will be: larger than smaller than equal to the original equilibrium partial pressure of SO2? 1.3) The immediate effect of the addition of H2O gas to the mixture is to: a) cause a spike decrease in the forward reaction rate b) cause a spike increase in the reverse reaction rate c) have no effect on the forward and reverse reaction rates 2) The reaction vessel is cooled from room temperature to -15.0 °C 2.1) The equilibrium constant would: increase decrease remain the same 2.2) The amount of NaHSOs(s) in the reaction vessel would: increase decrease remain the same 3) Some Na2SOs is added to the reaction vessel. increase decrease remain the same 3.1) The equilibrium constant would: increase decrease remain the same 3.2) The rate of the forward reaction would t) The volume of the container is decreased, thus increasing the pressure of all gases. shift left shift right no shift 4.1) The equilibrium will 5) Some of the SO, gas is removed from the reaction vessel. heat: absorb release impossible to tell 5.1) The system will 5.2) The immediate effect of the removal of SO2 is to: a) cause a spike decrease in the forward reaction rate b) cause a spike decrease in the reverse reaction rate c) cause a spike increase in the forward reaction rate
Explanation / Answer
Le Chatelier's principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change to reestablish an equilibrium. If a chemical reaction is at equilibrium and experiences a change in pressure, temperature, or concentration of products or reactants, the equilibrium shifts in the opposite direction to offset the change. This page covers changes to the position of equilibrium due to such changes and discusses briefly why catalysts have no effect on the equilibrium position.
So answering the questions --
1 =
1.1 = shift left
1.2 smaller than
1.3 a
2 =
2.1 = will remain same
2.2 = decrease
3 =
3.1 remain same
3.2 remian same
4=
shift left
5.1 increase or impossible to tell (bit confused here)
5.2 c
comment for clarification in any part. All the best
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