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 2.50 g of butane?
The exact molecular mass for butane (C4H10) is 12.0096*4+1.0079*10=58.1174 which is 58.1 to 3 significant figures.
Proportion of carbon in the compound 12.0096*4: 58.1174 => 48.0384 : 58.1174
The mass of carbon in 2.50 grams of butane can be obtained by proportion, namely Mass of carbon = 2.50 * (48.0384/58.1174) = 2.0664 = 2.07 g (approximated to 3 significant figures)
