Write the molecular formula of histamine

Histamine has the structure: $\text{C}_5\text{H}_9\text{N}_3$

Calculate its molar mass

Using approximate atomic masses: $\text{C} = 12, \quad \text{H} = 1, \quad \text{N} = 14$

So, $M = 5(12) + 9(1) + 3(14)$ $M = 60 + 9 + 42 = 111$

Mass of nitrogen in one mole of histamine

There are 3 nitrogen atoms, so mass of nitrogen is: $3 \times 14 = 42$

Calculate mass percentage of nitrogen

$\%N = \frac{42}{111} \times 100$

$\%N = 37.84\% \text{ (approximately)}$

Final answer

$\boxed{37.84}$

Comparison with stored correct answer

Stored correct answer range is: $37.80 \text{ to } 38.20$

Our answer, $37.84$, lies within this range. Hence it agrees with the stored correct answer.