Final answer:
It takes at least five hours for a person who is legally impaired with a blood alcohol concentration of .08% to sober up, as the metabolism of alcohol by the liver occurs at a consistent rate that is unaffected by external factors like drinking coffee.
Step-by-step explanation:
A person who is legally impaired with a blood alcohol concentration of .08% will need approximately five hours to become sober. This is because the human body, specifically the liver, metabolizes alcohol at a steady rate, which does not speed up with measures such as drinking coffee or taking a shower. While the legal limit leading to impairment is set at a BAC of 0.08, it's important to note that the rate at which alcohol is metabolized can vary between individuals due to factors such as sex and weight.
A general rate of alcohol metabolism is about 15 mg/dL per hour, but this can differ depending on the person's characteristics and the amount of alcohol consumed. For someone with a BAC of 0.08%, it would take their body to metabolize the alcohol and return to sobriety. It's critical for individuals to understand these limitations when consuming alcohol, especially if they plan to drive, as impairment can significantly reduce their ability to perform tasks that require skill and judgment.