Question

The atomic weight of two elements a and b are 20 and 40 respectively if x g of a contains y atoms how many moles are present in 3x g of b?

Answer 1

In case of same number of atoms,

(Mass of A) : (Mass of B) = 20 : 40 = 1 : 2

Now, (Mass of A) : (Mass of B) = x : 2x = 1 : 2

Then, they have the same number of atoms, i.e.

There are Y atoms of B.

Answer 2

$\huge\red{\boxed{\bold{Solutions}}}$

Number of moles of A = x/20.

Number of atoms of A = x/20 × N.

(N is the Av. Const)

Y = x/20 × N; x = 20y/N.

$\large\underline\mathrm\red{Further}$,

Number of moles of B = 2x/40,

Number of atoms of B = 2x/40 × N

$\implies$ 2N/40 × 20y/N

$\implies$ y.

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