Final answer:
To calculate the equilibrium moles of c from the mole fraction, additional information about the total number of moles in the mixture at equilibrium is required, which is not provided in the question.
Step-by-step explanation:
The student's question pertains to chemical equilibrium and mole fractions in a reaction described by the equation a + b → 3c. Assuming that c reaches an equilibrium mole fraction of 0.5 and the initial moles of a and b are each 2 moles, we would need to know the total number of moles in the mixture at equilibrium to calculate the equilibrium moles of c.
However, the question omits the necessary information to determine the total moles in the mixture at equilibrium, such as the volumes of the reactants or the total pressure of the system when dealing with gases if assuming ideal behavior.
Usually, the mole fraction is given by the ratio of the number of moles of a particular compound to the total number of moles in the mixture. Without this additional information, the equilibrium moles of c cannot be accurately determined.