. Find the mass of 2.61 moles of H2O2.

Mass of H₂O₂ = 88.778 g

The mole itself is the number of particles contained in a substance amounting to 6.02.10²³  

Mole can also be determined if the amount of substance mass and its molar mass is known

moles of H₂O₂ = 2.61

So the mass of H₂O₂(MW=34,0147 g/mol) :

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.