A solid sample of Zinc Hydroxide is added to 0.350 L of 0.500 M aqueous Hydrogen Bromide. The solution that remains is still acidic. It is then titrated with 0.500 M NaOH solution, and it takes 88.5 mL of the NaOH solution to reach the equivalence point. What mass of Zinc Hydroxide was added to the Hydrogen Bromide solution?

6.499 g

Explanation:

One part of the aqueous HBr reacted with Zinc Hydroxide following the reaction:

And the remaining HBr reacted with NaOH:

First we calculate how many HBr moles remained after reacting with Zn(OH)₂. That number equals the number of NaOH moles used in the titration:

Now we calculate how many moles of HBr reacted with Zn(OH)₂:

Then we convert those 130.75 mmoles of HBr to the Zn(OH)₂ moles they reacted with:

Finally we convert Zn(OH)₂ moles to grams: