Question

Question #1c86b

Answer 1

We recall that:

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

Define a general polyprotic acid, `"H"_n"A"`, 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)`

where `n` 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`.

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