Which of the following best describes the reaction quotient, Q, for a chemical system at a particular instant?
a) Q is the numerical value obtained when equilibrium concentrations are substituted into the equilibrium‐constant expression.
b) Q is the ratio of the activities of products to reactants, each raised to the power of its stoichiometric coefficient, evaluated with the current concentrations or partial pressures.
c) Q equals the instantaneous rate of the forward reaction divided by the rate of the reverse reaction at the same moment.
d) Q is the ratio of the initial concentrations of reactants to products, without regard to their stoichiometric coefficients.