Question

34.2ml of 2.0 M HCl(aq) is required to neutralise 25.0 ml of a Mg(OH)2 solution. What is the molarity of the magnesium hydroxide solution. (8 points)

Answer 1

First, we need the balanced equation to get the right # of moles of each compound. This is an acid-base reaction. soooo
HCl + Mg(OH)2 --> MgCl2 + H2O
Balanced: 2 HCl + Mg(OH)2 --> MgCl2 + 2 H2O

Answer 2

Now, you need to find how many moles of HCl we got. You can find it by manipulating this formula for molarity.:
\[Molarity (M) = \frac{ amount of moles }{ Volume (Liters) }\]

Answer 3

Make sure you use L, not mL.
When you find how many moles of HCl you have, use stoichiometry to figure out how many moles of Mg(OH)2 you need for a full reaction.

Answer 4

Finally, use the Molarity formula to find the molarity of the Mg(OH)2