Question

Explain how these problem are solved.(10th and 11th problem)

Answer 1

10 )

step 1:-
molar mass of compound /atom

so, molar mass of S8 = 32 x 8 = 256 g

given, weight of that compund ,
e.g weight of S8 given = 16g

step 2 :- find mole
mole = given wt /molar wt
= 16/256 = 1/16

hence , no of mole of S8 = 1/16

step 3 :-
no of atoms/ molecules/ions = mole of element /compund /ion × 6.023×10²³

now,
no of molecules = 1/16 ×6.023 × 10²³
=3.76 x 10²² .

11) aluminum is trivalent elements
so, Al attach with O in such way that 2mole of Al and 3 mole of O
.e.g Al2O3

in one mole of Al2O3 , 2mole Al+3 ions present .

now first we calculate ,
no of mole of Al2O3 = given wt /molar wt = 0.051/102 = 51 x 10^-3/102
=5 x 10^-4

hence, no of mole of Al2O3 = 5 x 10^-4

so, no of mole of Al+3 = 5 x 2 x 10^-4
= 10^-3 .

now,
no of ions = no of moles x 6.023×10²³
= 10^-3 × 6.023 ×10²³
=6.023 × 10^20