Chemistry Lab Report
Experiment 3: ANALYSIS OF UNKNOWN ACID SAMPLE USING TITRATION METHOD Date of Experiment: 4 September 2012
Introduction
An acid-base titration is a procedure used in quantitative chemical analysis to determine the concentration of either an acid or a base. Titration is the slow addition of an acid (or a base) of known concentration from a burette (a narrow graduated cylinder) to a base (or an acid) of unknown concentration fin an Erlenmeyer flask. There are two types of acids: strong acid and weak acid, and also two types of bases: strong base and weak base. Therefore four types of acid-base titrations are possible: strong acid-strong base, strong base-weak acid, weak acid-strong base and strong acid-weak base titrations. Acid + Base Salt + Water The end point occurs when the stoichiometric amount of base (or acid) has been added to the acid (or the base). The end point is frequently detected using a visual indicator. An acid-base indicator is a substance, which changes colour with pH. For each type of acid-base titration, an appropriate indicator must be chosen. However, the end point can also be determined potentiometrically using a pH meter or by a conductometric method. At this point, all the acid has been neutralized and neither excess base nor excess acid is present in the solution. The solution consists of salt and water only. That is why acid-base titrations are also called neutralization titrations (Sienko and Plane 1957, 340-343).
Neutralization reactions in experiments:
NaOH(aq) + KHP(aq) Na+ + KP- +H2O
NaOH(aq) + CH3COOH CH3COO- + Na+ +H2O
Infromation
- Some indicators (including Phenophthalein) Indicator | pH at which colour changes | Colour at lower pH | Colour at higher pH | Phenolphthalein | 9 | Colourless | Red | Litmus | 7 | Red | Blue | Alizarin Yellow | 11 | Yellow | Red | Methyl Red | 5 | Red | Yellow |
- KHP This is a large molecule
Introduction
An acid-base titration is a procedure used in quantitative chemical analysis to determine the concentration of either an acid or a base. Titration is the slow addition of an acid (or a base) of known concentration from a burette (a narrow graduated cylinder) to a base (or an acid) of unknown concentration fin an Erlenmeyer flask. There are two types of acids: strong acid and weak acid, and also two types of bases: strong base and weak base. Therefore four types of acid-base titrations are possible: strong acid-strong base, strong base-weak acid, weak acid-strong base and strong acid-weak base titrations. Acid + Base Salt + Water The end point occurs when the stoichiometric amount of base (or acid) has been added to the acid (or the base). The end point is frequently detected using a visual indicator. An acid-base indicator is a substance, which changes colour with pH. For each type of acid-base titration, an appropriate indicator must be chosen. However, the end point can also be determined potentiometrically using a pH meter or by a conductometric method. At this point, all the acid has been neutralized and neither excess base nor excess acid is present in the solution. The solution consists of salt and water only. That is why acid-base titrations are also called neutralization titrations (Sienko and Plane 1957, 340-343).
Neutralization reactions in experiments:
NaOH(aq) + KHP(aq) Na+ + KP- +H2O
NaOH(aq) + CH3COOH CH3COO- + Na+ +H2O
Infromation
- Some indicators (including Phenophthalein) Indicator | pH at which colour changes | Colour at lower pH | Colour at higher pH | Phenolphthalein | 9 | Colourless | Red | Litmus | 7 | Red | Blue | Alizarin Yellow | 11 | Yellow | Red | Methyl Red | 5 | Red | Yellow |
- KHP This is a large molecule
References: Acetic acid MSDS. 2012. “Material Safety Data Sheet Acetic acid MSDS.” Accessed September 3, http://www.sciencelab.com/msds.php?msdsId=9922769 Chemlab. 1997-2000. “Chemlab-glassware-burets.” Darmouth College. Sienko, Michell and Robert Plane. 1957. Chemistry. McGraw-Hill Book Company, Inc.