• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Determination of the relative atomic mass of Lithium.

Extracts from this document...

Introduction

Shimona Madalli 12A 15/02/03 Determination of the relative atomic mass of Lithium (Skills I, A and E) In this investigation, the aim is to determine the relative atomic mass of lithium, Li by two different methods: 1) By measuring the volume of hydrogen gas, H2 produced - METHOD 1 2) By titrating the lithium hydroxide, LiOH produced - METHOD 2 Skill I Hazards of method 1 and method 2 - All apparatus must be handled with care especially the glassware (e.g. conical flask) as can be broken easily. - Wear labcoat and safety goggles to avoid skin and eye contact with these chemicals. - The hydrochloric acid was dilute and as only 0.1M concentration was used the chemical acts as an irritant only. If spilled wash thoroughly with water and rinse eyes. - Hydrogen gas, H2 is a colourless and non - toxic, it is also flammable but as there were no naked flames this will not cause any risks. - Lithium is a very reactive metal. It is exothermic as it generates heat when involved in reactions. It is an irritant and so contact with this chemical should be avoided. - Lithium hydroxide, LiOH, is an alkali as well as an irritant. It also causes burns but as the solution is dilute this does not pose any problems. ...read more.

Middle

+ 2H2O (l) 2LiOH (aq) + H2 (g) Step 1 : Moles of hydrogen gas = volume produced 24000cm� 188cm� 24000cm� = 7.83 x 10-3 mol Step 2 : Mole ratio H2 : Li 1 : 2 7.83 x 10-3 mol : 0.016mol Step 3 : RAM of lithium = mass 0.09 = = 5.63 (prediction 6.92) moles 0.016mol Calculations : Method 2 - RAM of lithium Average titre = 12.6cm� + 12.4cm� + 12.5cm� = 12.5cm� (prediction 12.9cm3) 3 LiOH (aq) + HCL (aq) LiCl (aq) + H2O (l) Number of moles of LiOH present in 100cm� : Step 1: Moles of HCL = volume (cm�) x concentration (M) 1000 = 12.5cm� x 0.1M 1000 = 1.25 x 10-3 mol Step 2: Mole ratio HCL : LiOH 1 : 1 1.25 x 10-3 mol : 1.25 x 10-3 mol Step 3 : In 100cm� = 10 x (1.25 x 10-3 mol) = 0.0125mol I will use this result to calculate the RAM Step 4 : RAM of lithium, Li = mass Moles = 0.09g = 7.20 (prediction 6.92) 0.0125mol Skill E Overall the accuracy of my experiment was fairly consistent, for example all readings were to 3 significant figures. As you can see from the percentage errors (see below) method 2 was much more accurate. ...read more.

Conclusion

- this will surely increase the accuracy of the results. Limitation - It was very unclear when measuring initial and final amount of water in the measuring cylinder and so this would produce inaccuracies in the final volume of hydrogen gas produced. Improvement - Can use another piece of apparatus to improve the accuracy such as a gas syringe. Limitation - As the lithium metal was stored in oil, it was very difficult to remove all the oil and so this could of affected the actual mass of the metal. Improvement - Only solution to this is to measure the lithium metal many times. Or in an inert atmosphere, mix with hexane to remove oil and following this blow helium or nitrogen to remove the hexane. Comparison of methods 1 and 2 Comparing the two methods, method 2 which was the titration experiment was much more accurate. By using a graduated burette, the accuracy of my obtained results improved greatly which can be seen in my results table. Both methods are linked, if there were inaccuracies in method 1 then this would affect the accuracy of method 2. Relative error Relative error = Difference in figures Standard figure (in this case the standard figure is the standard RAM of lithium, which is '7') METHOD 1 : 7 - 5.63 X 100% = 19.6% 7 METHOD 2 : 7.20 - 7 X 100% = 2.86% 7 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Aqueous Chemistry essays

  1. Determination of Partition Coefficient

    0.03270 1.0 0.276 0.03752 1.1 0.262 0.03325 Table 3 Graph 1 From the graph, Kd = slope of graph = 0.13 With the standard value, percentage difference = = 13.3%.

  2. Determination of the relative atomic mass of magnesium by back titration

    Two concordant titres are required, if not, then repeats are taken. Method It is always important to remember that the method integrates ALL sources off error (as stated above), to increase accuracy. The method used is just a procedure, hence is kept simple, and one must recognize that we are constantly keeping ever fair.

  1. The Determination of an Equilibrium Constant.

    H2O = 18 g/mol Number of moles of H2O = 25 / 18 = 1.389 mole 2 Volume of NaOH used in titration is 17.4 cm3 Number of moles of OH- used = 0.2 / 1000 * 17.4 = 3.48 * 10-3 mole ?1 mole of H+ react with I

  2. How much Iron (II) in 100 grams of Spinach Oleracea?

    present in 100 grams of Spinach Oleracea the volume of moles in the 100cm3 spinach extract solution will need to be multiplied by 5. 0.001825 mol dm-3 X 5 = 0.009125 mol dm-3 Now that I know the moles present in 100 grams of spinach I can use the equation below to work out the mass of Iron (II)

  1. Determine the relative atomic mass of lithium.

    0.08 = mr 0.0125 mr = 6.40 the relative atomic mass of lithium according to this experiment is 64 Method 2 : Titration Apparatus 1 x Stand 1 x Clamp 1 x Burette 1 x Funnel 1 x Pipette filler 1 x Pipette (25cm�)

  2. Determination of the relative atomic mass of lithium.

    This anomaly may have been caused by a number of factors. The lithium is kept in oil while in storage to prevent it from oxidising. When using the lithium the oil must be cleaned off to ensure that it reacts to its full potential.

  1. Determination of the relative atomic mass of lithium.

    titration is 6.29 * Calculate the number of moles of LiOH present in 100 cm3 of the solution from method 1. * Use this result and the original mass of lithium to calculate the relative atomic mass of lithium. Evaluation The experiment I was given was not really accurate because

  2. Determination of the Relative Atomic Mass of Lithium

    Experiment 2 The results for the titrations are as follows; 28.3 cm3, 27.0 cm3 and 27.0 cm3. I will not take into account the first result because it is anomalous. Thus the average of the other two results is 27.0 cm3 It takes 27.0 cm3 of HCl to neutralise 25.0

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work