Question

1. what is true about the sysyem in chemical equilibrium?
a. the amount of reactant changes, but over time remains about the same
b. no reactants remain in the system
c. the amount of product equals the amount of reactant
d. there are no products in the system

Answer 1

none of those options are all that correct, IMO.

Answer 2

The options themselves seem to be a little bit vague. B and D are definitely incorrect, as if the reactants and products are in equilibrium then we can't have a case where one of them isn't there.

For option C, the concentration of the reactants and products will only be the same if the system is in complete equilibrium (neither the reactants or the products are favoured over one another) and there rate of the forward reaction = the rate of the backward reaction. However, we can have a system in equilibrium where either the reactants or the products are favoured over one another.

Option A also seems to be kind of correct in a sense as well. If we start with a certain amount of our reactant and it undergoes an equilibrium reaction, some of it will be converted to the product (forward reaction) and some will return to form the original reactant again (backward reaction). Once our equilibrium is established though over time, the amount of reactant present in our system should remain come down to a constant value.

For example, if we started with 10 moles of our reactant and proceeded with the reaction, we could be left with 4 moles of reactant and 6 moles of product once equilibrium is reached (or 5 and 5, or 3 and 7, and so on....). This specific amount would depend on the reaction itself and whether the product or reactants were favoured, but it should be fixed under fixed conditions.

Answer 3

If option A were changed to read "the amount of reactant changes \(rapidly \space at \space the \space start\), but over time remains about the same" that would be a better option.

Based on those options, I'd be forced to pick A, but I wouldn't like it