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Calculating Volume Needed for Level of pH

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A 1.00g sample of benzoic acid (C6H5CO2H, FW = 122.12g/mol,Ka = 6.5 x 10^ -5) is dissolved in water to give a solution with a volume of 500mL. What volume of 2.13M aqueous sodium benzoate (NaC6H5CO2) must be added to the aqueous benzoic acid solution to obtain a buffer with pH = 5.00?

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pH = pKa + log [sod.benzoate]/[benzoic acid]

[benzoic acid] = (1g/ 122.12g) x (1 mol / 0.500L) = ...

Solution Summary

The method to calculate the amount needed to make a buffer at pH 5 is shown.