8. When the liquid began to have swirls of yellow, I added the acid one drop at a time.
9. When the liquid became green, I stopped adding the hydrochloric acid and recorded the volume used to the nearest 0.05 cm3.
10. I repeated, recording the volume each time, until I had 3 values within 0.1 cm3 of each other.
11. If the solution turned yellow, then you have had added too much acid. Add 1 cm3 of sodium hydroxide, using a graduated pipette, then retitrate, adding one drop at a time of hydrochloric acid.
Results
For my titration practical I had 3 results, from which I worked out an average result.
To improve on the accuracy and reliability of my results, I had carried out my experiment twice. This ensures that my results are consistent, and therefore increases the reliability of them
Calculations
Reading 1= 21.9 cm3 reading 2=22.1 cm3 reading=21.8cm3
Calculation of average titre: 21.9+22.1+21.8= 65.8 cm3
65.8
3
Volume of alkali used=25 cm3
Concentration of alkali used=0.1 mol
Volume of acid used= 21.9 cm3
Analysis
Results for first experiment
25 x 0.1 mol
Results for second experiment
25 x 0.1 mol
23.3
Both of the results of my experiments are not far way from each other. However, they are not the same and there are several reasons for this which I will explain later in the evaluation section of this assignment. The readings which I gained for the first time I carried out my experiment are different to those which I gained in the second experiment.
Conclusion
In this practical, I was successfully able to perform a titration and now know what qualitative analysis is and have been able to form a technique of qualitative analysis. I was able to calculate the concentration of the acid used in this analysis. The results for both of the times when I carried out this practical are close to each other, although, the readings for the second time were not as close to the readings for the first time. I have also been able to find out that the acid which I was performing the titration on was more concentrated.
Vocational section
This section is about titration in industry. I will be writing an essay on titration in industry.
Titration in industry
A titration is a method in chemistry that allows quantitative analysis. By adding a reagent of known concentration until a reaction is completed (e.g. as shown by a colour change) the unknown concentration can be calculated. In this essay I will be talking about different types of titrations used in industry.
Titrations are routinely used in industry to analyse products to be sold. Many manufacturers are under strict standards of quality control because their products are sold for public consumption and so they do not want to harm the public. An example of this is titrations in the pharmaceutical industry, where you have to take special care in making sure the titration goes properly. Titrations require a lot more safety precautions as more harmful chemicals are used in industry. Titrations occur on a larger scale and only experienced and qualified scientists and chemist can perform these titrations.
There are 2 different types of titration’s, which I will be talking about this essay, acid-base titration and a redox titration
An acid-base titration is a method in chemistry that allows quantitative analysis of the concentration of an unknown acid or base solution. It makes use of the neutralisation reaction that occurs between acids and bases, and that we know how acids and bases will react if we know their formula. The key equipment used in this titration are, burette, pipette, acid-base indicator (the one used varies depending on the reactants), conical flask, Standard Solution (a solution of known concentration) and a solution of unkown concentration.
A redox titration also called oxidation-reduction titration or potentiometric titration) is a type of titration based on a redox reaction between the analyte and titrant. This titration relies on oxidation or reduction of the analyte. Both oxidation and reduction occur during a titration. A redox titration is a volumetric titration that relies on a net change in the oxidation number of one or more species.your titrant is commonly an oxidizing agent although reducing titrants can be used. The equivalence point is based on the concentration of the oxidized and reduced form of all species involved.
Some of this information has been used from www.google.com and www.wikipedia.com
Evaluation
During the course of my practical, I had encountered errors. These errors may have affected my final result and therefore it may have also made them inaccurate and unreliable.
The first error I occurred was when I was calculating the menicus. I may have not had the hydrochloric acid exactly on the meniscus and may have used too little or too much, which could also have affected my results. I was facing difficulty in reading the meniscus accurately. It occurred as it was located at the top of the burette. Although I made every effort to ensure that the meniscus was at the correct position, I may have made some errors of about 0.1 cm3, which will have affected my final result.
The second error which I may have made was judging when the colour change had occurred during my titration. Although the colour change had only occurred in a very short period of time, I may have stopped the tap for the burette later than it had actually occurred. This would have decreased the accuracy a reliability of my results as I may have been reading of a measurement which was not the correct measurement, instead was a later (larger, as the volume increases in size as you go down the burette) measurement.
The third error I may have made was that I had to repeat my practical as I had drawn in air bubbles when I was using the pipette to take in the sodium hydroxide solution. I then had to repeat my practical and carefully made sure that my pipette did not touch the surface of the beaker as I only dipped the pipette in slightly. However, after doing this carefully and ensuring I did not take in any air bubbles, my results were more accurate.
Errors may also have occurred when I was calculation how much of the sodium hydroxide solution I was bringing in to the pipette. I may have brought in too little or too much of the soltuion and this could have affected my results.
In this section of my assignment I will be evaluating my results and my practical.
Throughout my practical I had encountered problems and weaknesses. These may have affected my results and so may have altered the final result and conclusion given from my practical.
.
