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Half-Life's Order Dependence

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State

A first-order half-life stays constant throughout a reaction, but a second- or zero-order half-life changes as concentration falls.

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Hydrogen peroxide's first-order half-life stays six hours, while a second-order reaction's half-life grows longer as concentration drops.

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Assuming every half-life is constant, by analogy with first order, gives a wrong answer for other orders.