We’re being asked to determine the molecular formula of a compound composed of caffeine given the mass percent of C, H, N, and O. This means we need to do the following steps:
Step 1: Calculate the mass and moles of C, H, N and O in the compound.
Step 2: Determine the lowest whole number ratio of C, H, N and O to get the empirical formula.
Step 3: Get the ratio of the molar mass and empirical mass to determine the molecular formula.
Step 1: The compound is composed of C, H, N, O
C = 49.48%
H = 5.15%
N = 28.87%
O = 16.49%
Recall that mass percent is given by:
Assuming we have 100 g of the compound, this means we have 49.48 g C, 5.15 g H, 28.87 g N, and 16.49 g O. Now, we need to get the moles of each element in the compound. The atomic masses are 12 g/mol C, 1 g/mol H, 14g/mol N, and 16 g/mol O.
Calculating the molecular formula of caffeine? Caffeine, contains 49.48% Carbon, 5.15% Hydrogen, 28.87% nitrogen, 16.49% oxygen. It has a molar mass of 194.2 gmol-1.
Frequently Asked Questions
What scientific concept do you need to know in order to solve this problem?
Our tutors have indicated that to solve this problem you will need to apply the Empirical Formula concept. You can view video lessons to learn Empirical Formula. Or if you need more Empirical Formula practice, you can also practice Empirical Formula practice problems.