Which describes the state at which products form at the same rate as reactants?

chemical equilibrium

phase reversal

physical equilibrium

phase change

Chemical equilibrium is the state in which both reactants and products are present in concentrations which have no further tendency to change with time.
Or, we can say that in chemical equilibrium the  ratio between the concentration of the reactants and the products is constant.
Chemical equilibrium is a result state when the forward reaction proceeds at the same rate as the reverse reaction.
Different reactions have different equilibrium.

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.