Mass of water using isotopes? the water found on earth is almost entirely made up of the ^1h and ^{16}o isotopes for a formula of h_2o and a molecular mass of 18.0 amu. what is the largest mass that a water molecule could have using other isotopes?

Answer : 24.032 amu

Explanation : The mass of water using isotopes can be found by replacing the hydrogen element with its isotope called tritium which has mass of 3.016 amu.

Tritium (T) contains one proton and two neutrons in it. When the water is replaced by tritium the mass of the water becomes as;

= {(3.016 x 2) + 18} = 24.032 amu.

whereas in = {(1 x 2) + 18} = 20 amu.

So, the mass of water will be highest when we replace, hydrogen by tritium as the isotope.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.