Caffeine has an elemental analysis of 49.48% C,5.190% H,16.47% O,and 28.85% N.It has a molar mass of 194.19 g/mol.What is the molecular formula of caffeine?

Question

Quizplus · Accepted Answer

First, calculate the empirical formula:
- Divide the percent composition of each element by its atomic weight to get the ratio of each atom: C: 49.48/12.01 = 4.119, H: 5.190/1.008 = 5.157, O: 16.47/16.00 = 1.029, N: 28.85/14.01 = 2.063
- Divide each ratio by the smallest ratio to get whole number subscripts: C4.119H5.157O1.029N2.063 (rounded to the nearest whole number)
- The empirical formula is C4H5O1N2
Next, calculate the molecular formula:
- Divide the molar mass of caffeine by the molar mass of the empirical formula: 194.19/194.19 = 1
- The molecular formula is the same as the empirical formula: C4H5O1N2
- Multiply the subscripts by the integer obtained above: C4x1H5x1O1x1N2x1 = C4H5O1N2
- The molecular formula is B, which matches the calculated empirical formula.

Caffeine Has an Elemental Analysis of 49