When to ignore change in Acid
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Re: When to ignore change in Acid
You can ignore the change in acid concentration when Ka < 10-3, or when the change is 10-4 and lower. We assume that the change in acid concentration is negligible because it is a weak acid and will not completely ionize as a strong acid would.
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Re: When to ignore change in Acid
Yes, you would ignore the change in acid when the Ka value is less than 10^-3 because it is considered a weak acid and the change in concentration is so small that it can be ignored.
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Re: When to ignore change in Acid
However, always make sure to double check your approximation and ensure that change in x is less than 5% of the inital concentration!
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Re: When to ignore change in Acid
You can ignore the "x" or change in acid when Keq is less than 10^-3. However, after you find the equilibrium concentrations, you should check the % ionization or deprotonation of the acid/base. If it is less than 5%, then ignoring the change is valid.
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Re: When to ignore change in Acid
The standard way when using an ICE calculation, is to believe that if K is less than something x10^-3, we can assume it is 0 as it will have little to no effect on the calculation.
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