I know how to calculate average atomic mass, as well as the abundance of an isotope. How do I calculate the amu of an individual isotope given the average atomic mass? Is there an equation for this?

2H₂ + O₂ ⇒ 2H₂O

Further explanation

Conservation of mass states that

In a closed system, the masses before and after the reaction are the same

So it can be concluded

mass of the reactants = mass of the productsmass cannot be created or destroyedThe number of atoms involved in a reaction remains the same⇒ number of moles also the samechemical equation in balanced form

So let's see which of the several options , which one has the same number of atoms on both sides of the equation

2H₂ + O₂ ⇒ 2H₂O

H ⇒ left 4, right 4

O ⇒ left 2, right 2

so the equation is in balance and represents the Law of Conservation of

Mass