How many atoms are there in 5.7 mol of hafnium?

There are approximately 3.43 x 10^24 atoms in 5.7 mol of hafnium.

To calculate this, we first need to determine the molar mass of hafnium, which is 178.49 g/mol.

Next, we use Avogadro's number (6.022 x 10^23 atoms/mol) to convert the number of moles to atoms:

5.7 mol x 6.022 x 10^23 atoms/mol = 3.43 x 10^24 atoms