Question

How many atoms of Chlorine are present in 0.072g of FeCl3?

Answer 1

Approx. `8xx10^20` individual chlorine atoms...........

Explanation:

We (i) take the ration of the mass of the sample to the formula mass of `FeCl_3` to get the number of moles of `FeCl_3`.

`(0.072*g)/((55.85+3xx35.46)*g*mol^-1)=4.44xx10^-4*mol`.

And thus we have a molar quantity with respect to `FeCl_3`...the molar quantity with respect to `Cl` is CLEARLY three times this figure, i.e. `4.44xx10^-4*molxx3=1.33xx10^-3*mol`.....

But (ii) a mole specifies `"Avogadro's number"` of individual items of stuff, i.e. `N_A-=6.022xx10^23*mol^-1`.

And so ..........

`"number of chlorine atoms"=6.022xx10^23*mol^-1xx1.33xx10^-3*mol=??`