To determine the empirical formula of pentane, we can follow these steps:
Calculate the masses of carbon and hydrogen in the reaction products:
Mass of carbon in CO2 = (9.875 g CO2) x (1 mol C / 44.01 g CO2) x (12.01 g C / 1 mol C) = 0.814 g C
Mass of hydrogen in H2O = (3.745 g H2O) x (1 mol H2O / 18.02 g H2O) x (2 mol H / 1 mol H2O) x (1.01 g H / 1 mol H) = 0.518 g H
Determine the ratio of carbon to hydrogen in the empirical formula:
C:H ratio = 0.814 g C / 0.518 g H = 1.57
Determine the empirical formula:
We can round the C:H ratio to 1:1, and since the mass of pentane is 2.500 g, we can divide it by the sum of the masses of C and H in the empirical formula (1.335 g) to get the number of empirical formula units in the sample. This gives us approximately 1.88 units.
Therefore, the empirical formula of pentane is approximately C1H1, or just CH.
Note: The actual molecular formula of pentane is C5H12, but the question only asks for the empirical formula, which is the simplest whole-number ratio of atoms in a compound.
