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For problems where the textbook gives us the half-life of a second order reaction of a substance and it asks us to calculate the time needed for the concentration of the substance to decrease by 1/16, why can't we just multiply the half-life by 4 to get the time needed?
Sarah Zhao 4C wrote:You can't multiply it by four but you can square it by four!
Break down the math:
1/2 x 4 = 2
(1/2)^4 = 1/16
This doesn't give you the correct answer :( I think it's because, as someone said above, the half-life of a second-order reaction depends on how much reactant is left
you have to get the formula for t from the second rate equation which causes you to get t = (1/[A]t - 1/[A]o)/k and in this case you can replace [A]t with (1/16) x [A]o causing the equation to be t = (16/[A]o - 1/[A]o)/k and you just plug stuff in :)
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