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At 600 °C, a mixture of 0.5 moles of SO2, 0.12 moles of O2 and 5 moles of SO3 gases are placed in a

At 600 °C, a mixture of 0.5 moles of SO2, 0.12 moles of O2 and 5 moles of SO3 gases are placed in a 1 L vessel. When measurements are made some time later, the number of moles of each species are the same as the initial amounts. Which of the following statements is FALSE about this mixture?

A) The mixture is at chemical equilibrium.

B) There is no conversion of SO2 molecules to SO3 molecules occurring in the mixture.

C) The reaction between SO2 and O2 does not go to completion.


Explanation: When a reaction has reached equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction. Also, at equilibrium, the concentration of reactants and products remains constant. The reaction is still happening. Reactants are making products and products are making reactants back. We would not be able to observe it though since the rates of forward and reverse reactions are equal. Choice A can be eliminated since the reaction is at equilibrium and that is why concentrations remain constant. A reaction that is at equilibrium never goes to completion. Choice C is true as well. If a reaction goes to completion, reactants would simply make the most product possible and run out, stopping the reaction. B is false because the reaction is still taking place and SO2 molecules would be converted to SO3 molecules.

Answer: B


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