questions concernin calculation of mass of 1 mol of H+ ions.?

Question

Given question calculate the mass of 1 mol H+ ions.The mass of single electron is 9.1091x 10^-28.Given Avogadro's contant is 6.0225x10^23...Ar of H=1.0078g..

sltn given is by using equation of H -> H+ + e..
1.0078g - (6.0225+10^23)(9.1091 x 10^-28)
= 1.0073g..
my question is WHY the mass of electron has to be multiplied with avogadro's constant while the Ar of H need not to be multiplied with avogadro's constant?..

Answer 1

The Ar of H is Avogadro's number of H atoms. You need to take the mass of Avogadro's number of electrons away, so you have to multiply the mass of 1 electron by Avogadro's number.