Convert 1.25 x 1024 atoms of carbon to moles of carbon.

Explanation:

We are asked to convert a number of carbon atoms to moles.

We will use Avogadro's Number for this, which is 6.022 × 10²³. This is the number of particles (atoms, molecules, formula units, etc.) in 1 mole of a substance. For this problem, the particles are atoms of carbon. There are 6.022 ×10²³ atoms of carbon in 1 mole of carbon.

We will also use dimensional analysis to solve this problem. To do this, we use ratios. Set up a ratio using the underlined information.

We are converting 1.25 ×10²⁴ atoms of carbon to moles, so we multiply the ratio by that value.

Flip the ratio. It remains equivalent, but it allows us to cancel the units atoms of carbon.

The original measurement of atoms has three significant figures, so our answer must have the same. For the number we calculated, that is the hundredths place. The 5 in the thousandths place tells us to round the 7 up to an 8.

1.25 ×10²⁴ atoms of carbon is equal to approximately 2.08 moles of carbon.