# Problem: A solid sample of Zn(OH)2 is added to 0.310 L of 0.520 M aqueous HBr. The solution that remains is still acidic. It is then titrated with 0.520 M NaOH solution, and it takes 90.5 mL of the NaOH solution to reach the equivalence point.What mass of Zn(OH)2 was added to the HBr solution?

###### FREE Expert Solution

We’re asked to determine the mass of Zn(OH)that was added to 0.310 L of 0.520 M HBr solution, whose product is an acidic solution that was titrated with 90.5 mL of 0.520 M NaOH to reach the equivalence point.

Recall that at the equivalence point of a titration:

Also, recall that moles = molarity × volume

To solve for the mass of Zn(OH)2 we need to do these steps:

Step 1: Determine moles of NaOH at equivalence point to calculate moles of HBr in solution remaining after HBr reacts with Zn(OH)2

Step 2:Determine moles of HBr that reacted with Zn(OH)2

Step 3: Write a balanced equation for the reaction of Zn(OH)2 with HBr

Step 4: Determine mass of Zn(OH)2

The flow of the solution will be like this:

moles product (mole to mole comparison)→ moles Zn(OH)2 (molar mass Zn(OH)2 )→ mass  Zn(OH)2

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###### Problem Details

A solid sample of Zn(OH)2 is added to 0.310 L of 0.520 M aqueous HBr. The solution that remains is still acidic. It is then titrated with 0.520 M NaOH solution, and it takes 90.5 mL of the NaOH solution to reach the equivalence point.

What mass of Zn(OH)2 was added to the HBr solution?