Question

a 25 ml solution of H2SO4 is completely neutralized by 18ml of 1.0m of NaOH. What is the concentration of the H2SO4 soultion?

Answer 1

First, you want to convert the mL of NaOH to L. Afterwards you want to multiply it by its concentration to get moles. Since the moles of acid and base are equal to each other at the equivalence point (when the solution is neutralized), we can use the moles of NaOH to get moles of acid. Divide moles of acid by its volume in L to get the initial concentration of acid solution. Here's what it would look like:

Step 1: 18.0 mL NaOH/ 1000 L = 0.018 L NaOH

Step 2: (0.018 L)(1.0 M) = 0.018 moles NaOH

Step 3: Since moles of NaOH = moles of H2SO4, 0.018 moles H2SO4/0.025 L H2SO4 = 0.72 M H2SO4

So the initial concentration of H2SO4 is 0.72 M.