How many hydrogen atoms are there in 2.50 moles of C6H12O?

Avogadro's constant expresses the number of elementary entities per mole of substance and it has the value 6.02 × 1023 .

Thus there will be 2.5 times Avogadro's constant molecules of C6H12O present.

And as each molecule contains 12 atoms of Hydrogen

The number of atoms of Hydrogen present will be 12 times the product of 2.5 times Avogadro's constant.

= 1.806 * 1025 atoms of hydrogen.