Question

One uranium atom has a mass of `3.95 x 10^-22` grams. How would you work out an estimate for the number of uranium atoms in 1kg of uranium?

Answer 1

Well, we would calculate the quotient:

`(1xx10^3*g)/(3.95xx10^-22*g)=2.53xx10^24` `"uranium atoms"`

Explanation:

Alternatively, we could work out the molar quantity, knowing that `"Avogadro's number"`, `N_A` uranium atoms have a mass of `238.03*g`. We thus speak of the molar mass of uranium as `238.03*g*mol^-1`.

And thus `"moles of uranium"=(1000*g)/(238.03*g*mol^-1)=4.20*mol`.

And then multiply this molar quantity by `"the Avocado number"`:

`4.20*cancel(mol)xx6.022xx10^23*cancel(mol^-1)=??`

Should the numbers be the same? Are the numbers the same?