1. What is the atomic mass of hydrogen if 99.985% is hydrogen-1 and 0.015% is hydrogen-2?

The atomic mass of Hydrogen : 1.02985

Isotopes are elements that have the same Atomic Number (Proton)  

Atomic mass is the average atomic mass of all its isotopes  

In determining the mass of an atom, as a standard is the mass of 1 carbon-12 atom whose mass is 12 amu  

An atomic mass unit = amu is a relative atomic mass of 1/12 the mass of an atom of carbon-12.  

Mass atom X = mass isotope 1 . % + mass isotope 2.% ..

99.985% is hydrogen-1 and 0.015% is hydrogen-2

The atomic mass of Hydrogen :

your answer would be “dry”