Why does ascorbic acid change in concentration over time?
Can you give a little more detail? Under what conditions? How much time? Where did you hear this?
yup need more detail. If you are talking about a pill (though why you would be taking asorbic acid I don't know) the answer would be not much over long periods. In a solution (dissolved in water) it would get more concentrated as the water evaporates. Otherwise need more detail..
I'd surmise that this relates to ascorbic acid decomposing with time. The bottle of reagent powder then contains a mix of undecomposed ascorbic acid plus the solid products of decomposition. So you could say the grams of acid per teaspoonful of the powder falls with time.
In fruit juice, the ascorbic acid content oxidises, so this mechanism likewise decreases the ascorbic acid concentration with time.
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