Process of going through acid-base titration.
Aim
- Compute properties of the solution
- Analyze and interpret data
- Create a powerpoint presentation
Introduction
For one to determine the unknown concentration of an acid or base through neutralizing it with an acid or base of known concentration, we use the acid-base titration method. The reaction between an acid and a base to produce salt and neutralized base is known as neutralization .an acid whose conjugate base is much weaker than water is referred to as a strong acid. Strong acid dissociates completely in water to yield one hydrogen ions and a conjugate base. During titration, the concentration of substances in a solution is determined by adding amounts of other substances .the process continues until the endpoint when the colour of indicator changes. In calculating relative reactants and products in a chemical reaction, we apply the principle of stoichiometry. Basic chemical compounds that deprotonate weak acids in the acid-base reaction is known as a strong base. Sodium hydroxide and calcium hydroxides are examples or a strong base.
Phenolphthalein indicator is used when performing a strong acid strong base titration. Colour of phenolphthalein indicator changes between a ph range of 8 to 10. In basic solution, the colour changes to pink. In contrast, in acidic conditions, the colour becomes transparent. This transition takes a just a drop.burrete is used for the addition of these reactants. We use Erlenmeyer flask is where the reactant of unknown concentration is deposited.this compound is now referred to analyte.titran is placed in burette so that it can be delivered when the reaction starts. Phenolphthalein indicator is added to the analyte. for example, hydrochloric acid reacts with sodium hydroxide to form water and sodium chloride according to the equation below
HCL(ag) + NaOH(ag) H2O + NaCl(ag)
Thre are various indicators which are used in titration.methyl orange, methyl red and phenolphthalein indicators are used in strong acid against strong base titration. Also, the phenolphthalein indicator is used in weak acid against strong base titration.endpoint of this titration ranges between 8 to 10. Sodium acetate is hydrolyzed during this process of titration of acetic acid against sodium hydroxide.on the other hand. Methyl orange indicator is suitable for titration between a strong acid and a weak base, ph at the endpoint ranges between six to four. An example of strong acid against weak base titration is ammonium hydroxide against hydrochloric acid titration.
Apart fro using indicators to determine the end pint of titration, the potentiometer can also be used, its an instrument that measures the electrode potential pf the solution.these are used for redox titrations. The potential of the working electrode will suddenly change as the endpoint is reached.
Endpoint and equivalence point.
Though equivalence and endpoint are used interchangeably, they are different terms. Equivalence point refers to the theoretical completion of the reaction: the volume of added titrant at which the number of moles of titrant is equal to the number of moles of the analyte. Endpoint refers to what is measured, physical change in the solution as determined by the indicator or an instrument mentioned above.there is a slight difference between end pint and equivalence point of the titration. This error is referred to as indicator error, and it is indeterminate.
Titration curve
A titration curve is a curve in the plane whose x coordinates are the volume of titrant added since the beginning of the titration.y coordinates are the concentration of the analyte at the corresponding stage of the titration. In an acid-base titration, the curve reflects the strength of the corresponding acid and base. For strong acid strong base titration, the curve will be relatively smooth and very near the equivalence point. Due to this, a small change in titrant volume near the equivalence points results to a ph with massive change, and many indicators may be appropriate. On the other hand, titration of weak acid against the strong base, the titration curve will be irregular, and the ph will thus shift less to with small additions of titrant near the equivalence point. Titration curves corresponding to weak bases and strong acids are similarly behaved, with the solution being acidic at the equivalence point and indicators such as phenolphthalein.
Method and procedure
Reagents
Standard solution
Universal Indicators
Distilled water
A known volume of unknown concentration solution
Apparatus
Burette
Beakers
Pipette
Erlenmeyer flask
Clamp and stand
Funnel
Procedure
Use the standard solution to rinse the burette, unknown solution to rinse the pipette and distilled water to rinse the conical flask. Using the pipette, place an accurately measured solution into the Erlenmeyer flask. Add a few drops of indicator.clump the burette on a stand and put the standardized solution into it. Record the initial volume on a piece of paper. Run the solution out of the burette into the conical flask until the colour of indicator changes. Record the new reading of the burette in the piece of paper. Perform at least three titrations while keeping a record of the initial and final reading of the burette.take the difference between the initial and final readings accurately.
How to prepare a sample of an unknown acid.
Measure three samples of the unknown acid in three separate beakers. Add 25ml of distilled water to each beaker and swirl it gently to dissolve.
Table of results.
Discussion
Calculation of concentration of unknown acid.
As a scientist, titration is essential to my career. It equips a student with knowledge and understanding of titration in todays life.there are various fields in today life which involve titration. For example, in water waste analysis.titration, is used to determine the amount f contamination and the possible procedures required to put in place for cleaning and filtering of the wastewater. Advanced devices used in titration can measure the amount of harmful chemical substances present, reactant species in water as well as levels of the parasite [resent in the wastewater. Cleaning materials and sanitizers are courtesy of titration. Thus we use titration kits for the determination of chemical concentration in sanitizers and cleaning detergents.
Precaution
When conducting acid-base titration, students need to be very careful. Wearing a lab court is essential to avoid risks of getting burned by acids like sulphuric acid and other corrosive acids.students should take note that no open shoes are allowed in the laboratory. In the process of preparing unknown concentration of acid, understand that we add acid to water and not the other way round. Adding water to acids causes explosion and burns of faces and any other body parts. When using the pipette, students need to be careful to void swallowing laboratory chemicals. In case one swallows acid or base during titration, rinse with clean running water thoroughly to avoid health complication.
Recommendations
When experimenting in the lab, always observe proper chemical storage. Chemicals should be well labelled per industry guidelines. The laboratory should ensure adequate spacing between students and the setup experiments. Toxic chemicals should be documented together with their properties, which are hazardous to both personals and the environment. Emergency exits in the lab should be kept clear. Flammable substances should be handled with a lot of care. Incompatible chemicals should be rarely used when conducting experiments. Waste and chemicals which are hazardous which be well labelled using appropriate signs. The lab technicians should be aware of any working, which is shown in the lab. Equipment’s in the laboratory need to be adequate to avoid sharing among students.