Phys Sc Name___________________

Lab 3.1 Titration of an Acid with a Base Acidic Partner____________

Purpose: To neutralize a HCl solution of unknown concentration and to calculate its concentration from the volume of NaOH used.

Materials: burette, 250ml Erlenmeyer flask, 100ml beaker

Chemicals: HCl_(aq), NaOH _(aq), phenolphthalein

Procedure:

1. From the burette labeled "A" (A = acid), let out some HCl of unknown concentration into a waste beaker. This step will get rid of any air bubbles from the tip of the instrument.

2. Add more acid, and make sure that the bottom of the meniscus reads 0.00 mL. If not, either add more HCl, or pour some out.

3. Into a clean, dry erlenmeyer flask, pour out exactly 15.00 mL of acid.

4. Add 2 drops of phenolphthalein to the 15.00 ml of acid.

5. From the burette labeled "B" ( B = base), let out some NaOH whose concentration is 0.10 moles/L into a waste beaker. This step will get rid of any air bubbles from the tip of the instrument.

6. Make sure that the bottom of the meniscus reads 0.00 mL. If not, either add more NaOH, or pour some out.

7. Add the first 10mL of NaOH quickly, but be careful not to add more than 10.

8. Drop by drop, and while stirring constantly, slowly add more NaOH until the first permanent and light pink colour appears( it should last for 30 seconds; after that, it will gradually fade). Then stop.

9. Record this important volume of 0.10 M NaOH that's needed to neutralize the acid.__________________________

Analysis: Calculate the acid's concentration from the volume of base used. Since the ratio in which NaOH and HCl react is 1:1, we can use C₁V₁ = C₂V_2, where C₂ = unknown concentration of the acid ; V₂ = acid's volume; C₁ = base's concentration and V₁ = volume of base. Show calculations:

Conclusion: (One complete sentence = see purpose)