Question

Show your work and explain how you would find out how many liters of 0.500 M H3PO4 it would take to react with 8.00 L of 0.100 M NaOH.  

Answer 1

Given molarity of H3PO4 is 0.5M, volume=? and NaOH Molarity=0.1 M and volume=8 L.

Now find the moles of NaOH=Molarity x volume=0.1 moles/Lx8 L=0.8 moles.

The balanced equation between H3PO4 and NaOH is

H3PO4+3NaOH------>Na3PO4+3H2O

Therefore mole ratio between H3PO4 and NaOH is 1:3.

So moles of H3PO4=1/3(moles of NaOH)=1/3(0.8 moles)=0.266 moles H3PO4.

Given Molarity of H3PO4=0.5 M, so volume=moles/Molarity

Volume=0.266 moles/0.5 moles/L=0.533 L

So volume of H3PO4 is 0.533 L.

(Or) We can find out in another way

First convert Molarity into normality.

So normality of H3PO4=Molarity X3(since it has 3H's)=0.5x3=1.5 N, and for NaOH Molarity=normality (since it has 1 OH )

Therefore for NaOH 0.1 N and 8 L volume

From dilution law, N1V1=N2V2

1.5 NxV1=0.1 Nx8 L

V1=0.8/1.5=0.533 L.

So volume of H3PO4 is 0.533 L.