Question

The molar mass of nicotine is 162 grams. It contains 74% carbon, 8.7% hydrogen and 17.3% nitrogen? What is its empirical formula and its molecular formula?

Answer 1

C₁₀H₁₄N₂

Procedure

1. Find the molar mass of each component: C=12.0107, H=1.00794, N=14.0067

2. Convert to moles: C=6.16 H=8.63, N=1.24

3. Find the smallest mole value: 1.24

4. Divide all components by the smallest value: C=4.988, H=6.988, N=1

5. Divide by the fractional components (0.9883) of each mole value:

C=5.047, H=7.071, N=1.011

6. Round to closest whole numbers: C=5, H=7, N=1

7. Combine to get the empirical formula: C₅H₇N

8. Given that we have only half of the molecular weight we multiply the coefficients by 2.

The final formula is C₁₀H₁₄N₂