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:


moles acid=moles base


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?

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Strong Acid Strong Base Titrations concept. You can view video lessons to learn Strong Acid Strong Base Titrations. Or if you need more Strong Acid Strong Base Titrations practice, you can also practice Strong Acid Strong Base Titrations practice problems.

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Based on our data, we think this problem is relevant for Professor Marzal's class at UCF.