A 12.9 g sample of an aqueous solution of perchloric acid contains an unknown amount of the acid. If 10.7 mL of 0.338 M barium hydroxide are required to neutralize the perchloric acid, what is the percent by mass of perchloric acid in the mixture

Explanation:

Hello,

In this case, since the reaction between barium hydroxide and perchloric acid is:

It means there is a 2:1 mole ratio between the acid and the base; thus we compute the moles of barium hydroxide that are reacting:

Now, we compute the mass of perchloric acid (molar mass = 100.46 g/mol) by considering that 2:1 mole ratio:

Finally, the percent of perchloric acid in such sample is:

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4d^55s^1 ( third choice)