Question #41a9a

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, #"H"_3"O"^(+)#, or hydroxide anions, #"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 #"0.1-M"# solution will have a normality of #"0.2 N"#.

Consequently, you can say that a #"0.1-N"# solution will have a molarity of #"0.05 M"#.

So all you have to do now is figure out how many grams of acid must be dissolved in #"100 mL"# of solution in order to get a solution that is #"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 color(red)(cancel(color(black)("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.