"describe the equilibrium state of a reversible enzyme-catalyzed chemical reaction"

Answer is: the amount of substance of reactants and products of reaction do not change when chemical reaction is in chemical equilibrium.
In a chemical reaction, chemical equilibrium is the state in which both reactants and products are present in concentrations which not change with time. Speed of direct and irreversible chemical reaction are equal.

The air is going to come out because of the low pressure.

Non metal is an element or substance that is not a metal metal is a solid material that is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivitymetalloid is an element (e.g., germanium or silicon) whose properties are intermediate between those of metals and solid nonmetals. they are electrical semiconductors.