The fuel used in many disposable lighters is liquid butane, c4h10. butane has a molecular weight of 58.1 grams in one mole. how many carbon atoms are in 3.00 g of butane?

First, calculate the number of mols of C4H10 in 3.00 g of C4H10.

3.00g C4H10 / 58.1 g C4H10 = .0516 mol C4H10
There are 4 atoms of carbon per mol of C4H10
Multiply .0516 mol C4H10 by 4 (number of atoms of carbon)=.20654 mol Carbon.
To convert to atoms, multiply that by avogadro's number, 6.022 x 10^23
which equals 1.2438 x 10^23 atoms of Carbon