1. explain why matter must not be allowed to enter or leave a system if the system is to maintain chemical…

Brief Explanations:

Chemical equilibrium is a state where the rates of forward and reverse reactions are equal. If matter enters or leaves, it changes the concentrations of reactants and products. This disrupts the balance between forward and reverse reaction rates, thus altering the equilibrium state.

Answer:

Matter entering or leaving a system changes reactant and product concentrations, disrupting the equal - rate balance of forward and reverse reactions that defines chemical equilibrium.