Concentration of Solutions
Percent by Volume
Problem 5. A bottle of lambanog is 80 proof. What is the percent (v/v) of alcohol in this bottle of lambanog?
Answer
1. Known: proof number = 80
2. Unknown: % alcohol (v/v)
3. Process: Use the equation: proof number = % (v/v) × 2
By manipulating the equation:
\[
\begin{aligned}
\%\,\text{volume}
&=
\frac{
\text{proof number}
}{
2
}
\end{aligned}
\]
Therefore: %volume = 80/2 = 40
4. Answer: The 80-proof lambanog is 40% ethyl alcohol by volume.
