Question

What do you understand by mole? If, 8.4 g X element includes $9.03\times {10}^{22}$ atoms and 0.1 mol $X_2{Y}_3$ compound is 16 g, find atomic mass of Y element. (Avogadro number is $6.02\times {10}^{23})$

Answer 1

One mole is defined as the amount of substance containing as many elementary entities (atoms, molecules, ions, and more) as there are atoms in 12 grams of carbon-12. The number of particles that is atoms, ions, and molecules present in one mole of a substance is fixed with a value of $6.022\times {10}^{23}$.

number of moles of element X:
$n=\frac{Givennumber}{(6.02\times {10}^{23})}=\frac{(9.03\times {10}^{23})}{(6.02\times {10}^{23})}=0.15moles$

Atomic mass of element X:
$A_x=\frac{Givenmass}{No.ofmoles}=\frac{8.4}{0.15}=56g/mol$

Molar mass of $X_2{Y}_3$ compound:
$M_{X_2{Y}_3}=\frac{Givenmass}{No.ofmoles}=\frac{16}{0.1}=160g/mol$

We find atomic mass of Y,
2 x mass of X + 3 x mass of Y = 160
(2 x 56) + 3 x mass of Y = 160
Mass of Y = 16 g/mol