Oxygen-15, used in imaging brain function and blood flow, has a half-life of 2 min. How many half-lives have occurred in the 10 min it takes to prepare the sample?

Number of half lives = 5

Explanation:

Given data:

Half life of oxygen = 2 min

Half lives occured in 10 min = ?

Solution:

Formula;

Number of half lives = Time elapsed / half life

by putting values,

Number of half lives = 10 min / 2 min

Number of half lives = 5

it would be d. henry moseley

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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.