What mass of carbon is present in 8.02 x 10^23 formula units of Al2(CO3)3?

Answer 1

Use dimensional analysis:

formula units x moles/formula unit x moles C/mole x g C/mol C

8.02x10²³ formula units x 1 mole/6.02x10²³ formula units x3 mol C/mol Al₂(CO₃)₃ x 12 g C/mol C = 48.0 g (3 sig figs.)