The atomic weights of two elements A and B are 40 and 80 respectively. If x g of A contains y atoms, how many atoms are present in 2x g of B?

Number of moles of A =x40 Number of atoms of A=x40× Avogadro no. =y (say) Or x=40y Avogadro no. Number of moles of B =2x80Number of atoms of BB=2x80×Av. no. =280×40y Av. no. ×Av. no. =y