Question

If 10.0 mL of phosphoric acid solution required 23.5 mL of .200 M sodium hydroxide solution for neutralization to a phenolphthalein end point, calculate the molarity of the phosphoric acid.
H3PO4(aq)+3 NaOH (aq) --> Na3PO(aq)+3H2O

Answer 1

Step 1
use formula
molarity= mole/volume
molarity= mole/L
you have molarity and volume (convert to L) for NaOH
thus find mole of NaOH

Answer 2

Step 2
as you find mole of NaOH
work with ratio
what is the ratio between NaOH and H3PO4?
ratio can be found my looking at coefficients ( numbers before compounds, if there is no number written, that means its 1)

\[\frac{ mole ~of~ NaOH }{ coefficient~ of~ NaOH } =\frac{ mole ~of~ H_3PO_4 }{ coefficient ~ of ~H_3PO_4 }\]
thus find mole of H3PO4

Answer 3

Step 3
you found mole of Phosphoric acid and you have volume given to you (don't forget to convert to Liters)
so use formula
molarity = mole/volume
and get the final answer

Hope thats helpful :)

Answer 4

It did thank you!!!

Answer 5

you are welcome :))