Molecular Formula Video Lessons

Concept:

# Problem: 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.

###### FREE Expert Solution

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.

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###### Problem Details

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.