Question

terephthalic acid is a chemical used to make polyesters, including disposable water bottles. it has the empirical formula c₄h₃o₂. the molar mass of terephthalic acid is 166 g/mol. what is its molecular formula? answer: a c₄h₃o₂ b c₁₂h₉o₆ c c₈h₈o₈ d c₈h₆o₄ e c₁₀h₁₂o₈

Explanation:

Step1: Calculate empirical - formula mass

The empirical formula is $C_4H_3O_2$. The atomic masses of $C = 12\ g/mol$, $H=1\ g/mol$, and $O = 16\ g/mol$.
$M_{empirical}=(4\times12)+(3\times1)+(2\times16)=48 + 3+32=83\ g/mol$

Step2: Find the multiple $n$

The molar mass of the compound is $M = 166\ g/mol$.
$n=\frac{M}{M_{empirical}}=\frac{166\ g/mol}{83\ g/mol}=2$

Step3: Determine the molecular formula

Multiply the sub - scripts in the empirical formula by $n$.
The molecular formula is $(C_4H_3O_2)_2=C_8H_6O_4$

Answer:

D. $C_8H_6O_4$