What is true when a reaction has reached equilibrium?

the concentration of products and reactants is constant.

the reaction has stopped.

the concentration of the products is changing.

the concentration of the reactants is changing.

The concentration of the products and reactants is constant.

Explanation:

Once the reversible reaction that proceeds forward and backward simultaneously has reached it's state of chemical equlibrium, the concentration of products and reactants become constant.

This means that the rate at which the reactants react to form products becomes equal to the rate at which products react to form the reactants again. At this point there will be no further change in the concentration of reactants and products with time. In chemical equilibrium the concentration of a reactant or a product is expressed in moles per cubic decimeter ( mol / dm^3.

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally