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# Difficult Half-life question!!

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1. If the initial concentration in a first order reaction [would it be any different if it was a zero or a second order reaction??] with a half life of 12 minutes was 0.400 moldm-3, what would the concentration be after 48 minutes?
If the initial concentration in a first order reaction [would it be any different if it was a zero or a second order reaction??] with a half life of 12 minutes was 0.400 moldm-3, what would the concentration be after 48 minutes?
First order kinetics means that the half-life is constant. If it were any other order then the half live is dependent on the amount of substance.

Your question has four half-lives (48/12), therefore you halve the initial concentration four times.
3. (Original post by charco)
First order kinetics means that the half-life is constant. If it were any other order then the half live is dependent on the amount of substance.

Your question has four half-lives (48/12), therefore you halve the initial concentration four times.
I thought for second order reactions, half life doubles with halving concentration and for zero order reactions, half life halves with halving concentration. Is this wrong?

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