Final answer:
To find the volume of ethanol in a 25ml portion of mouthwash with 8.1% ethanol, multiply the mouthwash volume (25ml) by the ethanol percentage (0.081), resulting in 2.025ml of ethanol.
Step-by-step explanation:
To calculate the volume of ethanol in a 25ml portion of mouthwash with 8.1% ethanol, you multiply the total volume of the mouthwash by the percentage of ethanol. This calculation is based on the volume of solute (ethanol) over the volume of solution (mouthwash).
The formula for this calculation is as follows:
Volume of ethanol = Total volume of mouthwash × Percentage of ethanol
In this case, the calculation would be:
25ml × 0.081 = 2.025ml of ethanol
Therefore, a 25ml portion of mouthwash contains 2.025ml of ethanol.