Question

One atoms of an element x weigh 6.64310 -23 g. Number of moles in 20 kg is :

Answer 1

The mass of one mole of the atoms is equal to 6.023 x 6.643 Therefore no. Of moles in 20000 g= 20000/6.023x 6.643 = 499.8.

Answer 2

Answer : The number of moles of an element x in 20 Kg is, 500 moles.

Solution : Given,

Mass of an element x = $6.64310\times 10^{-23}g$

First we have to calculate the mass of an element x.

1 mole of an element x contains $(6.022\times 10^{23})\times (6.64310\times 10^{-23}g)=40g$ of an element x

Now we have to calculate the number of moles of an element x.

As, 40 grams of an element x present in 1 mole of an element x

So, 20,000 grams of an element x present in $\frac{20000}{40}=500$ moles of an element x

Therefore, the number of moles of an element x in 20 Kg is, 500 moles.