Question #1c86b

1 Answer
May 17, 2017

We recall that:

"Molarity" = "mols solute"/"L solution"Molarity=mols soluteL solution

Define a general polyprotic acid, "H"_n"A"HnA, whose complete dissociation would be represented as:

"H"_color(red)(n)"A" + color(red)(n)"H"_2"O"(l) -> color(red)(n)"H"_3"O"^(+)(aq) + "A"^(color(red)(n)-)(aq)HnA+nH2O(l)nH3O+(aq)+An(aq)

where nn is the number of protons in the acid.

Then, its normality is:

" "ul(" "" "" "" "" "" "" "" "" "" "" "" "" "" ")
" "ulbb(|" ""Normality" = color(red)(n) xx "Molarity"" "| )

In a context that you might actually use, consider a polyprotic acid, such as "H"_3"PO"_4.

For example, if we have a "1 M" molarity, then we actually have a "3 N" normality, because it takes "3 mol"s of "OH"^(-) to neutralize "1 mol" of "H"_3"PO"_4.

Or, define a general hydroxide-containing strong base, "B"("OH")_n (where "B" is the base, not boron). Then, its complete dissociation would be represented as:

"B"("OH")_(color(red)(n))(aq) -> "B"^(color(red)(n)+)(aq) + color(red)(n)"OH"^(-)(aq)

Then, its normality is also as defined above.

For example, if we have a "2 M" molarity of "Ba"("OH")_2, then we actually have a "4 N" normality, because it takes "4 mol"s of "H"^(+) to neutralize "2 mols" of "Ba"("OH")_2.


As a note, the normality unit is discouraged by IUPAC and NIST due to its ambiguity and dependence on context.