# What is the percent by mass of the magnesium hydroxide?

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A 0.5895 g sample of impure magnesium hydroxide is dissolved in 100.0 mL of 0.2050 M HCl solution. The excess acid needs 19.85 mL of 0.1020 M NaOH for neutralization.

A 0.5895 g sample of impure magnesium hydroxide is dissolved in 100.0 mL of 0.2050 M HCl solution. The excess acid needs 19.85 mL of 0.1020 M NaOH for neutralization.

##### 1 Answer

#### Answer:

The sample is 91.42% magnesium hydroxide.

#### Explanation:

Let us first work out how many moles of acid were neutralized by the sample.

Beginning:

After the sample was added:

We are given the amount of

Now each me of the added

so we have:

So we started with 0.02050 mol

Now we can work out how mych magnesium hydroxide must have neutealuzed that acid. Start with the balanced equation:

So then:

We weighed the sample in grams so calculate the grams of magnesium hydroxide using the molecular or formula weight

This is how much magnesium hydroxide is in the