Question on a Kaplan sample test

[cc609]

1. Concentrated sulfuric acid is 18M. What volume of water would be needed to dilute 25mL of concentrated H2SO4 solution to 3M?
a. 25mL
b. 50mL
c. 75mL
d. 125mL
e. 150mL

The answer is 125 which I understand now with the explanation they provided (The M1V1=M2V2), but I just learned about Normality vs Molarity...apparently not well though 🙁 Why don't we multiply the molarities by 2 and use Normality for the equation N1V1= N2V2 since H2SO4 has 2 Hs? When exactly do we use normality then if it's not used in this case? Thank you in advance!

 

[hurley]

.

 

[virajpatel]

yeah thats strange how come normality isnt applied?

 

[gn4]

I believe you mostly use normality when trying to mix an acid and a base.

 

[Piepiesuperpie]

I think you only use normality (N1V1 = N2V2) for titration/equivalence point since you're comparing your acid to base. Since this is a dilution problem, it's the same compound. You CAN use normality, but the normality would cancel out because it's the same compound.

 

[haiKUHN]

You don't multiply by 2 because only the first H in H2SO4 is really acidic and contributes to the acidic nature of sulfuric acid. Essentially, the acid contribution from the second H is negligible.