Question

Total number of electrons in 81g of al3+

Answer 1

As given Al3+
(Which means has loosed 3 e-mail )
Atomic no.=13
Electron remaining=10
27g=atomic mass
27g of Al3+=10Na
1gof Al3+=10Na/27
81gof Al3+=10*6.02*10^23*81/27=
1.806*10^25

Answer 2

answer : 1.8069 × 10^25

number of electron in Aluminium element, Al = 13

now, when we remove three electron from Al it becomes Al³+ ion. and then number of electrons in one Al³+ ion = 13 - 3 = 10....(1)

now, atomic mass of Aluminium or Al³+ ion = 27 g/mol. [ you should remember that if we remove or add electron to any element, mass number doesn't change. ]

given mass of Al³+ = 81g

so, number of mole of Al³+ = 81/27 = 3mol

then, number of Al³+ ions in 3 mol = 3 × 6.023 × 10²³ = 18.069 × 10²³

now, number of electrons in 18.069 × 10²³ Al³+ ions = 10 × 18.069 × 10²³ [ from equation (1), ]

= 1.8069 × 10^25