Worksheet: Concentration Changes in Equilibria

In this worksheet, we will practice calculating changes in the concentrations of reactants and products due to shifts in the position of equilibrium.

Q1:

Consider the following equilibrium. 4NO()+6HO()4NH()+7O()2232gggg

Which of the following is the correct expression for the equilibrium constant (𝐾c) of the reaction?

  • A𝐾=[][][[]c3222NHONO]HO
  • B𝐾=[][][][]c22324NO6HO4NH7O
  • C𝐾=[][][]c3222NHONO[HO]
  • D𝐾=[][][][]c2232NOHONHO
  • E𝐾=[][][[]c32224NH7O4NO]6HO

How must the concentration of NH3 change to reach equilibrium if the reaction quotient is less than the equilibrium constant?

  • AIncrease
  • BDecrease
  • CStay the same

If the reaction were at equilibrium, how would a decrease in pressure (from an increase in the volume of the reaction vessel) change the pressure of NO2?

  • AStay the same
  • BDecrease
  • CIncrease

If the change in the pressure of NO2 is 28 torr as a mixture of the four gases reaches equilibrium, how much would the pressure of O2 have changed?

Q2:

A suspension contains solid Mg(OH)2 in equilibrium with dissolved Mg2+ and OH ions. If solid KOH is added to the suspension, which of the following effects is not observed?

  • A[Mg]2+ decreases.
  • B[OH] decreases.
  • CThe pH increases.
  • D[K]+ increases.
  • EThe amount of solid Mg(OH)2 increases.

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