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Determining the atomic mass of lithium from method one. After setting up my apparatus, I went on to measure my Lithium metal

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Introduction

Safety Prior to starting this experiment, I wrote a risk assessment which covered the possible risks and hazards associated with practical and how to avoid them. I know that lithium is highly flammable and reacts vigorously with water to produce lithium hydroxide which is an irritant and can coarse serious damage if it gets into the eyes. Hydrochloric acid is also corrosive and irritant. To avoid these hazards I wore eye protection throughout the experiment. I also wore a lab coat to protect any acid from spilling on my clothes and gloves to protect my hands. Fair test * Lithium is immersed in paraffin therefore I will dry it before weighing to avoid taking a wrong weight which might affect the reliability of my final result. * I will also to set up my apparatus before putting the lithium in to the water and quickly place the bang so as to reduce the risk of loosing any gas * I will ensure that all the apparatus are rinsed with distilled water first then where possible with chemical it is to contain. This is to reduce the risk of contamination. ...read more.

Middle

When phenolphthalein indicator is added to the lithium hydroxide solution, it changes the colour into pink. In the titration there is a point where the colour will change from pink to still-grey. This is the end point and it is at this point that I took the burette's reading. My first titration (rough) was to give me a rough idea of where this point is so that I will be more careful with the rest when it nears the same volume by running the titration drop by drop. This will improve the accuracy of my results. I also repeated the titration of three times which improves the reliability of my results and read the bottom of the meniscus when taking readings and took it to the nearest 0.05cm3 for better precision and accuracy RESULTS No. of titre Start (in cm3) Finish (in cm3) Average titre (in cm3) Rough 0.00 28.85 28.85 1st 0.00 28.50 28.50 2nd 0.00 28.45 28.45 3rd 0.00 28.50 28.50 Mean titration = (28.50+28.45+28.50) � 3 = 28.48cm3 Calculating no of moles of HCl No. of moles = concentration x volume Volume of HCl = 28.48cm3 = 0.02848dm3 Concentration = 0.100dm3 ==> 0.100 � 0.02848 = 0.002848moles From here I will find the number of moles of LiOH The balanced chemical equation bellow shows the reaction between Lithium Hydroxide and Hydrochloric acid. ...read more.

Conclusion

The only thing I could have done was to ensure every thing was set up before taking out the Li and quicken the drying and measuring of it * Another problem that could have affected the reliability of my final result was the equipments. Most of the equipments I used were class B. this could have affected accuracy of the measurement reading I could avoid this by using class A equipments so that the reading is as accurate as possible. Collecting the gas in a gas syringe could also give more accurate readings. * There could be errors when reading the level of the burette and visually checking for the point at which the solution turned from pink to colourless. This fault is almost impossible to eradicate. * It was required that only 5 drops of indicator were added, this was done carefully but the sizes of each drop may differ from the other, although very minimal this could affect the final result. Adding 20 drops to the 100cm� before taking out anything would have ensured even distribution of the indicator * Another problem was weighting the lithium. As it was stored under oil for it's reactive nature ?? ?? ?? ?? 1 Zakaria Dahir ...read more.

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