Q 12.36 - An Introduction to General, Organic, and Biological Chemistry

Question

Avobenzone is a common ingredient in sunscreen. Its structural formula is shown. 

a. What functional groups are in avobenzone? 

b. What is the molecular formula and molar mass of avobenzone? 

c. If a bottle of sunscreen containing$236$ mL has$3.0\%$ (m/v) avobenzone, how many grams of avobenzone are present?

Step-by-Step Solution

Answer

(a) The functional groups present in the avobenzone are thiol and ketone.

(b) The molecular formula is${\mathrm{C}}_{20}{\mathrm{H}}_{22}{\mathrm{O}}_3$ and the molar mass is$310\mathrm{g}$.

(c) $7.08g$of avobenzone are present.

Part (a) Step 1: Given information

We are given the compound and we have to find out the functional groups present in it.

Part (a) Step 2: Explanation

The compound avobenzone contains${\mathrm{CH}}_3-\mathrm{O}-{\mathrm{CH}}_3 \mathrm{and} {\mathrm{CH}}_3-\mathrm{C}\left(=\mathrm{O}\right)-{\mathrm{CH}}_3$ and in this first one is a thiol functional group, and the another one is a ketonic group.

Hence, thiol, and ketonic functional groups are present in avobenzone.

Part (b) Step 1: Given information

We are given the compound and we have to find out the molecular formula and molar mass of this compound.

Part (b) Step 2: Explanation

The compound oxybenzone contains twenty carbons, twenty two hydrogens, and three oxygens, which states that the molecular formula of oxybenzone is $C_{20}{H}_{22}{O}_3$and the molar mass of oxybenzone is$mass= 20\times 12+22\times 1+3\times 16=310g$.

Hence, the molecular formula is$C_{20}{H}_{22}{O}_3$ and the molar mass is$310g$. 

Part (c) Step 1: Given information

We are given the volume and mass per volume of avobenzone and we have to find out the mass of avobenzone.

Part (c) Step 2: Explanation

The bottle of sunscreen contains $236 ml$$3.0\%\left(m/v\right)$ and to find out the mass

$m/v\%=\frac{mass of solute}{volume of solution}$

Putting the value we get, $\frac{3}{100}=\frac{mass}{236}$

On solving we get, $mass=7.08g$.

Hence, the mass of oxybenzone is$7.08g$.