Question

How many formula units of sodium carbonate are in 2.87 moles?

Answer 1

Formula units are another way of expressing "molecules". One mole is equivalent to
`6.022*10^(23)`.

Use dimensional analysis to solve this problem.

2.87 moles
`* (6.022 *10^(23) molecules)/(mole)`

Then, cross off the moles in the given number and the denominator, and your remaining unit is molecules of sodium carbonate.

Then, multiply and divide accordingly to the fraction.

2.87 * 6.022*10^23 = 1.72 * 10^24. Notice how the given problem has only 3 sig figs, so the answer should also have 3 sig figs

Your final answer would be 1.72
`*10^(24)` formula units of sodium carbonate.