How many atoms of carbon would there be in 5.56g diamond?

There would be 2.79 x 10^23 carbon atoms.

Explanation:

Diamonds are made of carbon. You're given mass and want to convert to number of atoms. The common way to convert between these and other variables is through moles.

First find moles by dividing the mass by the molar mass (of carbon):

moles = 5.56 / 12 = 0.463

Next multiply moles by Avogadro's number to find the number of carbon atoms:

number of C atoms = 0.463 x 6.022 x 10^23 = 2.79 x 10^23