Acid-Base Titration Lab

Acid-Base Titration Lab

Introduction:

In chemistry there is a range of different reactions but of the most common ones is a neutralization reaction between an acid and a base. During a neutralization reaction an acid is mixed with a base until the acid becomes neutral and has a pH of 7. In this experiment the reaction was between Hydrochloric Acid and Sodium Hydroxide.

1HCl (aq) + 1NaOH (aq) 1H2O (l) + 1NaCl (aq)

The products of a neutralization reaction are salt and water, which forms due to a combination of hydronium and hydroxide ions in an aqueous solution. When the Hydrochloric Acid combines with the sodium hydroxide in the correct amount the concentration of hydrogen ions is equal to the concentration of hydroxide ions and the base has neutralized the acid.

H+ (aq) + OH-(aq) H2O (l)

During this acid and base titration a neutralization reaction was used to correctly find the unknown concentration of Hydrochloric Acid from a known concentration of Sodium Hydroxide. This process is known as standardization. A process known as titration is used to correctly determine the amount of volume of a titrant needed to react with an analyte (McGraw-Hill Ryerson, 679). A titrant is solution with a known concentration and an analyte is a solution undergoing testing to find the unknown concentration When titration is done correctly an equivalence point is reached meaning stoichiometrically the same amount of both solutions has been added(McGraw-Hill Ryerson, 675). During titration phenolphthalein is placed into the acid as an indicator to exactly determine when the sodium hydroxide has neutralized the hydrochloric acid. The colour change in titration represents an "end point" which is the exact moment when the sodium hydroxide has neutralized the hydrochloric acid (McGraw-Hill Ryerson, 675). If the end point was reached correctly the solution will turn a light pink colour, if the solution has been over titrated the solution will turn a dark pink colour which is bad in this experiment.

To find the concentration of the unknown acid after the titration has ended, will be very simple using our balanced chemical equation and a simple formula. From the balanced chemical equation we can see that there is a 1:1 molar ratio between the sodium Hydroxide and the Hydrochloric acid so knowing the concentration and volume of the base we can determine the unknown concentration of the acid. The formula used to calculate the concentration of the hydrochloric acid is VaCa=VbCb. In this formula the V stands for volume, the C stands for concentration and the "a" and "b" stand for acid and base. When we plug in all the known variables we can easily isolate the concentration of hydrochloric acid and solve with a simple one step calculation.

Purpose:

The purpose of this lab is to correctly determine the equivalence point between Hydrochloric Acid and Sodium Hydroxide. Also, to calculate the concentration of the HCl solution and find the end point between sodium hydroxide and hydrochloric acid.

Hypothesis:

By the end of the titration reaction between Hydrochloric Acid and Sodium Hydroxide the solution would be neutralized and a permanent colour change would occur showing the end point. Since the Sodium Hydroxide reacts with exact same amount of Hydrochloric acid, one can use the known concentration of the Sodium Hydroxide to find the unknown concentration of the Hydrochloric acid using the formula VaCa=VbCb assuming the volume of the Sodium Hydroxide and Hydrochloric acid is known.

1HCl (aq) + 1NaOH (aq) 1H2O (l) + 1NaCl (aq)

VaCa=VbCb

(20ml)(Ca) = (8.0ml)(1.00 Mol/L)

(20ml) (20ml)

Ca = 0.4 mol/L

The Concentration of Hydrochloric Acid is 0.4 Mol/L

Materials:

* 100 ml Buret

* Buret Stand

* Buret Clamp

* 150ml Erlenmeyer flask

* Sheet of plain white paper

* Safety Goggles

* 25ml Graduated Cylinder

* Sodium Hydroxide Solution (1 Mol/L)

* Hydrochloric Acid (20ml)

* Distilled Water

* Phenolphthalein Dropper (3 drops)

Safety:

During the experiment goggles must be worn at all times to protect the eyes from chemicals such as Hydrochloric Acid and Sodium Hydroxide. Also after the lab, before dispensing any acids or bases down the sink make sure to neutralize them carefully and pour down the sink with plenty of water. During the experiment if any chemicals are spilled on the counter they must be reported to the teacher for proper clean up procedure.

Procedure:

1. Information gathered from the teacher was recorded on a lined piece of paper

2. A chart was copied into our notebooks and used to make observations

3. Safety Goggles were worn at all times during experiment

4. Using a graduated cylinder 20ml of hydrochloric Acid was measured and added to a clean 150ml Erlenmeyer flask.

5. Using a graduated cylinder 10ml of distilled water was measured and carefully added to the Erlenmeyer flask containing Hydrochloric Acid

6. 3 drops of phenolphthalein were added into the same Erlenmeyer flask from a dropper bottle

7. The Erlenmeyer flask was shaken to thoroughly mix the solution

8. The Erlenmeyer Flask was placed under the tip of the buret and placed on a white sheet of paper

9. The initial volume of the sodium hydroxide from the buret was observed and recorded

10. Titration was started by slowly adding sodium hydroxide into the Erlenmeyer flask in small amounts and carefully swirling the Erlenmeyer flask. Water was added to the sides of the Erlenmeyer flask to make sure base had not been stuck on the sides. When the solution changed to a light pink colour the end point was reached.(If the solution had