Results
Assume that 1 mole of gas occupies 24000cm3 at room temperature and pressure.
<Equation>
Calculate the number of moles of hydrogen
Ratio of Lithium ~> Hydrogen is 2:1
Volume
Vol. of gas = 170/24000 = 0.00708333 mols of Hydrogen
Deduce the number of moles of lithium
Lithium = 2 x Hydrogen mols
= 0.0147666
Calculate the Ram of lithium
RAM = 0.1
0.0141666 RAM = 7.06
Apparatus
- Burette
- White tile
- 250cm3 Conical flask
- Funnel
- 10cm3 pipette
Diagram
Method 2
- Begin by washing out the burette, funnel and pipette with water and also the solution that will be passed through. Make sure the tap is closed when filling up the burette.
- Set up the equipment as shown above
- Fill the burette to the 0cm3 mark, with the bottom of the meniscus touching the top of the line. Allow the tap to run, releasing any air bubbles and will also clean the tip of the burette.
- Once it has been filled with the acid (HCl). Measure out 10cm3 of the LiOH using a 10cm3 pipette and put it in to the conical flask
- Add five drops of phenolphthalein indicator, once placed in the alkali it will turn a pink/magenta colour.
- Begin by adding the acid 2 or 3cm3 at a time. The first titration should be a rough titration. Once the colour changes, it should go colourless as it reaches a neutral solution, record the value at which the acid is in the burette.
- Refill the burette and repeat the task, adding 10-12cm3 first, then adding the drop by drop, until the final few drops, remembering to swirl it after each drop. Record your results in a table.
<TABLE>
Results
Volume of HCl = Average titre = 14
- 1000 = 0.014dm3
Ratio 1:1 of HCl:LiOH
Concentration = 0.1Molar
Number of moles of HCl in the titration
Number of moles = Concentration x Volume
= 0.1 x 0.014
= 0.0014
Deduce the number of moles of LiOH in the titration
Number of moles of LiOH = 0.0014
Number of moles of LiOH present in 100cm3 of the solution in method 1
10cm3 solution = 10 x 0.0014
= 0.014
Calculate the RAM of lithium
RAM = Mass
No. Moles = 0.1/0.014
RAM = 7.142857143
Method 1 Accuracy = +-7.06/6.95 x 100 = 101.58% = 1.58% error
Method 2 Accuracy = +-7.143/6.95 x 100 = 102.7769784 = 2.78% error
Percentage error - Method 1
Measuring cylinder to measure 100cm3 water = 1/100 x 100%= 1%
Measuring cylinder to measure 170cm3 H2 gas =1/170 x 100% = 0.59%
=+-1.59%
Method 2
Burette to measure 3 titres of 25 + 3 readings of about 14cm3
= 0.15/25 x 100% x 3 = 0.6 x 3 = 1.8%
= 0.15/14 x 100% x 3 = 1.07 x 3 = 3.21%
Pipette to measure 3 x 10cm3 = 0.05/10x100% = 0.5 x 3 = 1.5%
=+-6.51%
Evaluation
- The overall results of my experiments are quite both accurate. Allowing for the inaccuracy of the equipment I was using, informs me that there was no human error in my results. The main sources of error were the equipment.
