HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) Lab 26 Date: Titration of HCl Purpose Determine the molarity of HCl using standardized NaOH Background HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) ?? M 0.1M 0.1 M NaOH – 4.0 g NaOH in 1 L soln 0.12 M HCl – 10 mL 12M HCl in 1 L soln 10.0 mL Titrate (dictionary) – to ascertain the quantity of a given constituent by adding a liquid reagent of known strength and measuring the volume necessary to convert the constituent through a given reaction. Titrate (our version) – to determine the concentration of solution by using a solution with a known concentration.

Experiment - Clean a buret with soap and water and then ‘prep’ the buret with about 5 mL of 0.10 M NaOH. Using a funnel, fill the buret to the 0.00 mL mark with 0.10 M NaOH. Pipet 10.0 mL of the HCl solution into a clean Erlenmeyer flask. Add 2 drops of phenolphthalein. Titrate the HCl slowly until the pink endpoint. Record the final volume of NaOH used. Repeat the titration 2 more times.

Analysis Which solution was more concentrated? Explain how you know. Which solution was the standard in this lab? Calculate the average volume of NaOH that was used to titrate the HCl; convert this to liters. Calculate the molarity of the HCl Why should the first titration trial be performed slower than the 2nd or 3rd trials. Results -

Questions - What is the formula for molarity? One liter of 0.1M NaOH contains how many moles? How many liters of 0.1M HCl are required to neutralize 1 L of 0.1M NaOH? How many mL of 0.1M NaOH are required to neutralize 100 mL of 0.5M HCl? If 10.0 mL of NaOH reacts with 10.0 mL of HCl, what can be assumed about their concentrations?