What is the molar mass for 2H2O?

There is no such thing as a molar mass of 2H₂O.
The molar mass is by course-is-taught-exclusively-on-line-you-need-to-read-and-understand-material-that-is-presented-please-read-chapters-5-6-as-indicated-on-the-syllabus-and-then-submit-the-five-m/”>definition the mass of one mole.
The mass of 1 mol of H₂O is (2×1.008 + 1×15.999) g = 18.015 g.
So the molar mass of water is 18.015 g/mol.
Of course, the mass of 2 mol of water is
##2 cancel(“mol”) × “18.015 g”/(1 cancel(“mol”)) = “36.030 g”##.
But that’s not the molar mass of 2H₂O.