How many molecules are in 2.50 mole of h2o?

1.5×1024 molecules.

Explanation:

You can calculate the number of molecules from moles by using Avogadro's constant, 6.02×1023molecules/mol.

For every 1 mol, there are 6.02×1023 molecules.

Simply multiply

2.5 mol×6.02×10231 mol=1.5×1024 molecules

Same as 2.50 moles of anything. multiply number of moles by avagadro’s numberino:
(2.50)6.022e23=1.51e24