Chemistry / Unit 9 Chem 1675 short lesson, about 20 seconds
Half-Life's Order Dependence
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The idea
A first-order half-life stays constant throughout a reaction, but a second- or zero-order half-life changes as concentration falls.
In practice
Hydrogen peroxide's first-order half-life stays six hours, while a second-order reaction's half-life grows longer as concentration drops.
Where people slip
Assuming every half-life is constant, by analogy with first order, gives a wrong answer for other orders.
Your place on the trail
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