Final answer:
Ethanol can be detected in the blood shortly after alcohol consumption, with concentrations peaking within 30 minutes to 2 hours. A Breathalyzer can accurately measure the amount of ethanol present, using a color-change reaction, and the metabolism of ethanol occurs at a constant rate independent of its concentration.
Step-by-step explanation:
The concentration of ethanol in the blood can be detected shortly after the consumption of alcoholic beverages, with its levels peaking usually within 30 minutes to 2 hours, depending on various factors such as the amount and rate of alcohol intake, metabolism, and individual differences in physiology. The substance is then metabolized by the liver, where a zeroth-order reaction takes place, meaning the rate at which ethanol is oxidized is constant and independent of its concentration in the blood, until the ethanol is nearly depleted. Detection and measurement are commonly conducted through the use of devices like Breathalyzers, which utilize a chemical reaction that results in a color change corresponding to the ethanol amount present in the breath sample, reflecting the blood alcohol concentration (BAC).
Legally, alcohol intoxication is often defined as a BAC greater than 0.025-0.080%. The oxidation of ethanol by the dichromate ions in a Breathalyzer causes a color change from yellow-orange to green, the intensity of which can be compared with standard solutions to determine the ethanol concentration in the person's breath accurately. Over time, the ethanol concentration decreases linearly, which is indicative of a zeroth-order reaction, until it drops to essentially zero, at which point the reaction rate falls rapidly.