Q116CP - Chemistry: Molecular Nature Of Matter And Change

Question

Serotonin ( µ=176 g/mol) transmits nerve impulses between neurons. It contains 68.2 mass % C, 6.86 mass % H, 15.9 mass % N, and 9.08 mass % O. What is its molecular formula?

Step-by-Step Solution

Answer

The molecular formula is C₁₀H₁₂N₂O.

Step 1: Calculating the moles

On multiplying the reciprocal of molar mass to convert mass into moles,

$\begin{array}{l}Moles of C=68.2 g C\times \frac{1 mol C}{12.01 g C}=5.68 molC\\ Moles of H=6.86 g C\times \frac{1 mol H}{1.01 g H}=6.79 mol H\\ Moles of N=15.9 g C\times \frac{1 mol N}{14.01 g N}=1.13 mol N\\ Moles of O=9.08g O\times \frac{1 mol O}{16 g O}=0.57 molO\end{array}$

Step 2: Calculating the molecular formula

On dividing all subscripts,

$C_{\frac{5.68}{0.57}}{H}_{\frac{6.79}{0.57}}{N}_{\frac{1.13}{0.57}}{O}_{\frac{0.57}{0.57}}\to C_{10}{H}_{12}{N}_{2}O$

The mass of empirical mass can be denoted as,

$\begin{array}{l}=10\times 12.01 g/mol+12\times 1.01 g/mol+2\times 14.01 g/mol+16 g/mol\\ =176.24 g/mol\end{array}$