Question

how many moles of retinol (c₂₀h₃₀o), a form of vitamin a, are in a 0.125 g sample of retinol? select the correct answer below: o 4.36×10⁻⁴ mol o 35.8 mol o 3286.4 mol o 2290 mol

Explanation:

Step1: Calculate molar - mass of retinol

The molar - mass of $C_{20}H_{30}O$:
The atomic mass of $C = 12.01\text{ g/mol}$, $H=1.01\text{ g/mol}$, and $O = 16.00\text{ g/mol}$.
$M=(20\times12.01 + 30\times1.01+1\times16.00)\text{ g/mol}$
$M=(240.2+30.3 + 16.00)\text{ g/mol}=286.5\text{ g/mol}$

Step2: Use the mole formula

The formula for the number of moles $n=\frac{m}{M}$, where $m$ is the mass and $M$ is the molar - mass.
Given $m = 0.125\text{ g}$ and $M = 286.5\text{ g/mol}$
$n=\frac{0.125\text{ g}}{286.5\text{ g/mol}}\approx4.36\times 10^{-4}\text{ mol}$

Answer:

A. $4.36\times 10^{-4}\text{ mol}$