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Sodium carbonate is an irritant to the skin and eyes so it is important to wear gloves and safety googles as well as wash hands if contact is made.
To start we had to make sure we calibrated our equipment this means we had to make sure it was reading 0 before starting, to do this a known weight was placed on the scales to make sure it was correct and if not we moved a screw to make sure it was adjusted correctly.
We also made sure that when the weighing boat was placed on we removed the weight on the boat or we readjusted to make sure we allowed for the boat when placed on.
The equipment which will be used for this small segment of the experiment is a weighing scales, beaker, distilled water, a glass rod and a measuring cylinder. All of the equipment which is used is rinsed and washed to prevent any contamination of previous substances which could affect the end result of the mixture created.
4.9 (984)
“ Ok, let me say I’m extremely satisfy with the result while it was a last minute thing. I really enjoy the effort put in. ”
The sodium carbonate is weighed out (1.44g) and is put into a beaker, the distilled water is then added to the beaker and a glass rod is used to stir the mixture. Once the mixture is stirred fully it is poured out into the graduated flask and topped up to 250 cm3 for the standardisation.
Mass of sodium carbonate = 1.44g
Mr of sodium carbonate = 106
1.44/106 = 0.01358 moles in 250cm3
Potential errors: In the practical there could have been errors this could be with the room temperature or even in the weighing of the substances this means it could have not been as accurate as we would have liked it to be.
Using more than 1 person when weighing or measuring by eye can differ the results this is because they could have different in eye sight meaning what one person thinks it is another person thinks it’s something else.
Standardisation of Hydrochloric acid using sodium carbonate solution
This can be done by sucking up distilled water, to the graduated line then transferring the water to the beaker which has been zeroed on a balance. We can then identify the mass of water helped by the pipette and the burette and compare it to the volume Stated on the apparatus. The pipette volume was very accurate reading 25.0032cm3 and so was the burette at 50.019cm3. These values were close enough to give overall accurate reading.
Throughout the experiment dangerous chemicals are handled therefore to ensure maximum protection and safety for conduction the experiment hazard clothing such as; goggles for eye protection, gloves for hand protection, lab coats to protect clothes and all hair and ties pinned back to avoid knocking over any equipment while the experiment is carried out. All of the equipment was rinsed before and after use to avoid any contamination with previous experiment and leftover chemicals.
Hydrochloric acid is corrosive so contact with skin should be controlled.
Average = 15+14.3+14.4+14.5+14.1+14=86.3/6=14.3 cm3
Moles of sodium carbonate in 25cm3 = 0.01358/10 = 0.001358 moles
1:2 ratio 0.001358 moles x 2 = 0.002716 moles
Concentration of HCl = 0.002717/14.3/1000 = 0.19 mol/dm3
Actual concentration of HCl was 0.2 mol/dm3 so our result was reasonably accurate.
Titration of unknown sodium hydroxide solution using standardisehydrochloric acid
The health and safety of this experiment is the same as the sodium carbonate, therefore basic protections for each aspect of the person conducting the experiment as well as extra precaution taken for the harmful and acidic substances being handled in the experiment.
The titration follows the method of 6 main steps;
It was important to carry out a trial run to see if there would be any problems and we then did repeats to ensure accurate results. Any anomalous results were not counted in the average.
Average = 14.6+14.1+14+13.2+14.7+13.8+13.5=97.9/7=14 cm3
Moles of HCl – 14/1000 x 0.19 = 0.00266
Moles of NaOH = 0.00266 moles
Concentration of NaOH = 0.00266/ (25/1000) = 0.1064 mol/dm3
Through the calculations above the concentration of the sodium hydroxide was worked out to be 0.1 064 mol/dm3 which again shows an accurate technique as the actual concentration of NaOH was 0.1 mol/dm3.
There are results in both tables that could be recognised as errors, for example; the results that deviate too far from the average of 14. Table 1 shows this by the trial run being 15 which is slightly inaccurate to the average of 14.3. Another example is on table 2 where result 3 comes out at 13.2, far smaller than the average titre of 14.
There could have been improvement made to the experiment which would have made the experiment pinpoint accurate by using specialised and accurate equipment such as glass pipettes, to control how much acid is used and not have it relied on inaccurate human reactions which would affect the end result and increase the amount of overall titre used in the experiment.
When comparing my results to others who done the experiment at the same time as me as well as following the same method the results recorded were very similar to my own, the results came out at 14.17cm3 for the standardising of the hydrochloric acid which very close to my average of 14.3cm3. The averages recorded for the titration of sodium hydroxide standard solution using standardisedhydrochloric acid was 13.56cm3 from my peers results, which when compared to my results is 0.44cm3 lower than my average of 14cm3. This can be seen as evidence to the fact that my experiment was carried out correctly and with the others having around the same number increases the validity of the results as well as proving that the experiment is reproducible. When comparing the results closely to each other the anomalies were identified with ease and were not taken into account for the average.
Titration of Sodium hydroxide with Hydrochloric Acid using pH meter
The calibration in this experiment is specific towards the use of the pH meter, the pH meter is calibrated by a using a method to ensure accurate results;
As we increase the volume of acid the pH value falls, from 0cm to 11cm it was an alkaline, however, the solution neutralised from 12 to 13. If the experiment was redone the volume of the acid could start around 12 to get more accurate pH readings for when the solution is neutralised.
The point of neutralisation for my set of results was around 12cm3 which is lower than that of the titration reading.
Moles of HCl – 12/1000 x 0.19 = 0.00228
Moles of NaOH = 0.00228 moles
Concentration of NaOH = 0.00228/ (25/1000) = 0.0912 mol/dm3
The actual concentration of sodium hydroxide was 0.1mol/dm3 From the two methods we see that the first titration of sodium hydroxide and the hydrochloric acid is more accurate than the other. Because it gave a result of exactly 0.1mol/dm3 whereas the PH value wasn’t too far off it was slightly below at 0.9mol/dm3
With carrying out titration we could have made improvements this means measuring with the eye shouldn’t have been done and should have been looked at doing electronic this means that it could have been measured to an exact line and not guessed, this is because different angles looking at a line could show it to be at different heights. Furthermore with the stirring we would do it till we think it was dissolved this means that we couldn’t tell that it was all dissolved but with an electronic stirrer it would be able to do it much faster and more accurate meaning it would have a more chance of being mixed.
Making copper sulfate standard solution
Mr = 63.5 + 32 + (4 x 16) + (5 x 18) = 249.5 to make 0.1 M in 1000cm3
Mass = moles x Mr = 0.1 x 249.5 = 24.95g in 1000cm3 / 10 = 2.495g in 100cm3
Making dilutions
Concentration M
Volume of copper sulfate cm3
Volume of water cm3
Colorimetry is a tame experiment therefore there is not many safety precautions to take into account, if the colorimeter uses a UV bulb then UV absorption goggles should be used as well as care to not look directly at the bulb due to possible retina damage. The UV bulb could also shatter due to hot spots created by oil from fingers therefore the bulb should not be handled without proper procedures. Also to prevent damage to the machines the test tubes being put into the colorimeter should be dry and not wet.
This graph shows that the absorption increased when the concentration of copper sulphate solution increases. Although all of the graphs results look average and fit in there is an anomaly on the graph at 0.3-0.4. The result for 0.3 is 0.854 and the trend so far has been consistently an increase of 0.2nm every 0.1M of CuSO4, However 0.4 is 1.202 which is an increase of 0.4nm rather than the 0.2nm increase consistent in previous results. Due to this 0.4 is an error in the results and is an anomaly which could be to the fault of a colorimetry error in the experiment.
Unknown samples
The possible colorimetry errors that could have occurred can be related to human error or faulty equipment. The Human error could have occurred at any point in the experiment that relied on the reactions of a person like pouring the liquids and mixing the solutions. Equipment errors could occur in the colorimeter not reading the results correctly or something wrong with the glass tubes holding the solutions.
Analyzing Chemical Solutions: Methods, Results, and Evaluation. (2024, Feb 19). Retrieved from https://studymoose.com/document/analyzing-chemical-solutions-methods-results-and-evaluation
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