Explain how these statements differ, and identify which one(s) is/are correct. Explain what is wrong with each incorrect statement.

Question

A. A chemical reaction is at equilibrium when there is no further change in substrates.
B. A chemical reaction is at equilibrium when the amounts of substrates and product no longer change.
C. A chemical reaction stops when it reaches equilibrium.
D. A chemical reaction is at equilibrium when the amount of substrate equals the amount of product.

Answer 1

Only B is correct as written. A could be corrected by clarifying that it is concentration or amount of substrate that ceases to change; individual molecules can form or break at any given time, but the overall amount will not change because synthesis will be balanced by degradation. C is incorrect because the reactions continue as long as conditions such as presence of catalysts, favorable temperature, and presence of substrates are maintained. As a given enzyme can both synthesize and degrade, both processes will continue even at equilibrium. D is incorrect because at equilibrium there is no net change in amounts, but it is not necessary for concentrations of substrates and products to be the same as each other.