Under Henry's Law, at a given temperature, the amount of alcohol in the air is proportional to the amount in which solution?

Under Henry's Law, at a given temperature, the amount of alcohol in the air is proportional to the amount in which solution?

• A. Water solution
• B. Blood
• C. Urine
• D. Saliva

Answer: (A)

Henry's Law says that at a constant temperature, the amount of a volatile substance dissolved in a liquid is proportional to the partial pressure of that substance in the gas above the liquid. In the lungs, ethanol equilibrates between the blood and the alveolar air. This means the amount of alcohol in the exhaled air is proportional to the amount in the blood. The breath sample therefore reflects blood alcohol concentration, not urine or saliva, and not simply a generic water solution. Breathalyzers use this blood–air partition relationship (often cited as about 2100:1) to estimate how much alcohol is in the blood.

Henry's Law says that at a constant temperature, the amount of a volatile substance dissolved in a liquid is proportional to the partial pressure of that substance in the gas above the liquid. In the lungs, ethanol equilibrates between the blood and the alveolar air. This means the amount of alcohol in the exhaled air is proportional to the amount in the blood. The breath sample therefore reflects blood alcohol concentration, not urine or saliva, and not simply a generic water solution. Breathalyzers use this blood–air partition relationship (often cited as about 2100:1) to estimate how much alcohol is in the blood.