It is found that an average volume of 24.25 ml of approximately 0.1 M NaOH is required to reach an endpoint in a titration with 25.00ml of 0.09917 M HCl solution. What is the NaOH concentration? Make sure to give answer to four significant figures.

Answer 1

NaOH + HCl ==> NaCl + H2O
mols HCl = M x L = ?
mols NaOH = mols HCl (since the reaction shows 1 mol HCl = 1 mol NaOH
Then M NaOH = mols NaOH/L NaOH. The problem is confusing because it appears there is no unknown; ignore the "approximately 0.1 M NaOH". That's the unknown. That's what you're calculating in the last step.