# Question 41a9a

Jul 20, 2017

$\text{1 g}$

#### Explanation:

The thing to remember about a solution's normality is that it depends on the nature of the reaction.

In an acid-base reaction, a solution's normality is a measure of the concentration of hydronium cations, ${\text{H"_3"O}}^{+}$, or hydroxide anions, ${\text{OH}}^{-}$, present in the solution.

In your case, you know that the acid is dibasic, which implies that it can donate $2$ protons in an acid-base reaction. This means that for every $1$ mole of acid, you get $2$ moles of hydronium cations.

So in this case, a $\text{0.1-M}$ solution will have a normality of $\text{0.2 N}$.

Consequently, you can say that a $\text{0.1-N}$ solution will have a molarity of $\text{0.05 M}$.

So all you have to do now is figure out how many grams of acid must be dissolved in $\text{100 mL}$ of solution in order to get a solution that is $\text{0.05 M}$.

100 color(red)(cancel(color(black)("mL solution"))) * overbrace("0.05 moles acid"/(10^3color(red)(cancel(color(black)("mL solution")))))^(color(blue)("= 0.05 M")) = "0.005 moles acid"#

To convert this to grams, use the molar mass of the acid

$0.005 \textcolor{red}{\cancel{\textcolor{b l a c k}{\text{moles acid"))) * "200 g"/(1color(red)(cancel(color(black)("mole acid")))) = color(darkgreen)(ul(color(black)("1 g}}}}$

The answer is rounded to one significant figure.