As with any drug, aspirin (acetylsalicylic acid) must remain in the bloodstream long enough to be effective. assume that the removal of aspirin from the bloodstream into the urine is a first-order reaction, with a half-life of about 3 hours. the instructions on an aspirin bottle say to take 1 or 2 tablets every 4 hours. if a person takes 1 aspirin tablet, how much aspirin remains in the bloodstream when it is time for the second dose? (a standard tablet contains 400. mg of aspirin.)

180 mg

Explanation:

For a first-order reaction, we can calculate the amount of aspirine (A) at a certain time (t) using the following expression.

where,

k: rate constant

A₀: initial amount

If we know the half-life () we can calculate the rate constant.

When t = 4 h and A₀ = 400 mg, A is:

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answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.