Problem: A 0.5890 g sample of impure magnesium hydroxide is dissolved in 103.0 mL of 0.2040 M HCl solution. The excess acid then needs 19.88 mL of 0.1036 M NaOH for neutralization.Calculate the percent by mass of magnesium hydroxide in the sample, assuming that it is the only substance reacting with the HCl solution.  Express your answer using four significant figures.

FREE Expert Solution

Recall that at the equivalence point of a titration:


moles acid=moles base


Also, recall that moles = molarity × volume


There are 2 equivalence points:


  1. Mg(OH)2  + 2HCl  → MgCl2 + 2H2O
  2. HCl + NaOH → NaCl + H2O


moles base = moles acid - moles HClexcess (2nd equiv.)



molesacid=MVacid



For 1st equiv. point:

  • 2 moles HCl react with 1 mole Mg(OH)2
81% (498 ratings)
View Complete Written Solution
Problem Details

A 0.5890 g sample of impure magnesium hydroxide is dissolved in 103.0 mL of 0.2040 M HCl solution. The excess acid then needs 19.88 mL of 0.1036 M NaOH for neutralization.

Calculate the percent by mass of magnesium hydroxide in the sample, assuming that it is the only substance reacting with the HCl solution.  Express your answer using four significant figures.

Frequently Asked Questions

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 Solution Stoichiometry concept. You can view video lessons to learn Solution Stoichiometry. Or if you need more Solution Stoichiometry practice, you can also practice Solution Stoichiometry practice problems.