# A solution contains 10.0 m mol of H_3PO_4 and 5.0 mmol of NaH_2PO_4. How many millimeters of 0.10...

## Question:

A solution contains {eq}\rm 10.0\ m mol {/eq} of {eq}\rm H_3PO_4 {/eq} and {eq}\rm 5.0\ mmol {/eq} of {eq}\rm NaH_2PO_4 {/eq}. How many millimeters of {eq}\rm 0.10\ M\ NaOH {/eq} must be added to reach the second equivalence point of the titration of the {eq}\rm H_3PO_4 {/eq} with {eq}\rm NaOH {/eq}?

## Equivalence Point:

The equivalence point in an acid-base titration is when chemically equivalent quantities of acid and base have been mixed. For the titration of a triprotic acid with sodium hydroxide this is sometimes referred to as "first equivalence point", "second equivalence point", etc. Each of these points can be represented as a separate reaction equation, and they will each require a 1:1 molar ratio.

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The first equivalence reaction is:

{eq}H_3PO_4 + NaOH \rightarrow H_2O + NaH_2PO_4 {/eq}

• moles of {eq}H_3PO_4 {/eq} remaining = {eq}0.0100 mol...