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Solution: An acetaminophen suspension for infants contains 80 mg/0.80 ...


An acetaminophen suspension for infants contains 80 mg/0.80 mL suspension. The recommended dose is 15 mg/ kg body weight. How many mL of this suspension should be given to an infant weighing 14 lb? (Assume two significant figures.) 

Video Transcript

Hey guys, in this question we're told that we have an acetaminophen solution or suspension for infants and it is composed of 80 milligrams of the prescription drug for every 0.80 ml of suspension, we're also told the recommended dosage is 15 milligrams per kilogram of body weight so 15 milligrams per 1 kilogram of body weight then we're asked how many milliliters of suspension are necessary for an infant that weighs 14 pounds so we're given a lot of numbers, a lot figures so we're going to go step by step and see what the best approach to take in order to get this answer correct so we should start out with 14 pounds because it's just one unit by itself easier to manipulate instead of something that has two units mixed in, OK? So, we have 14 pounds, now we're looking for milliliters, milliliters are right here so we need to isolate those mls and the way we're going to isolate those mls is by canceling out these milligrams, those milligrams can be canceled out by these milligrams. Now the body weight of the infant is 14 pounds we can't use pounds right now because we need to change it into kilograms so it can cancel out with these kilograms of body weight so we're going to say for every 1 pound we have 453.592 grams. Next we have to change grams to kilograms so grams go on the bottom kilograms go on top kilos is a metric prefix so 1 kilo is 10^3, grams cancel out now we have kilograms and now that we have kilograms we can finally cancel out these kilograms here so we have 15 milligrams for every 1 kilogram of body weight, kilograms cancel out so we're left with milligrams and finally we cancel out these milligrams in the 80 so 80 milligrams goes on the bottom and then point 80 mls of solution goes on top, when we work that out we realize here that 80 has an infinite number of sig figs so we're going to ignore that but 0.8 and 15 both have 2 sig figs so our answer at the end has 2 sig figs would be 0.95 mls of suspension so that would be our final answer here. So again we have a lot of units being thrown at us it's best to start out with the one that has one unit by itself easier to manipulate and then you should always start by writing what they're asking you to find and all then all the given information and do what we do here, draw a line trace a line because the information I'm asking you for can always be found in some way within the given information you just have to draw a path to it knowing which way to go will help you to figure out how to set up the dimensional analysis setup and in that way units cancel out and you'll get your answer at the end.