• 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 magnesium by back titration

Extracts from this document...


Determination of the relative atomic mass of magnesium by back titration Introduction / Aim In this following experiment, we are aiming to determine the relative atomic mass of magnesium, using a process known as 'back titration'. The basic outlines of this experiment include a strip of magnesium being allowed to reach with excess hydrochloric acid. The excess acid is then determined by titration with a standard alkali (Sodium Hydroxide) and hence the moles of acid that reacted with the magnesium is found by difference. This can be used to determine the number of mole of magnesium used (explained more thoroughly in analysis section). The relevant equation is: 2H+ (aq) + Mg (s) --> Mg2+ (aq) + H2 (g) Safety Precautions Chemical / Apparatus Hazard Precaution Hydrochloric acid Irritant Avoid contact with skin, handle with care, wash off any spileges, wear eye protection. Sodium Hydroxide Irritant See above Methyl orange indicator Stains Handle with care, avoid contact with skin Apparatus * 250cm3 volumetric flask * 25cm3 pipette * Pipette filler * Burette * Burette clamp with stand * 250cm3 conical flash * White tile Reagents * Clean magnesium ribbon * Standard 1.0M hydrochloric acid solution * Indicator (screened methyl orange) ...read more.


This results in more frequent, successful collisions. ****BRIGGS*** Never had time to finish this part off. Varied The volume of standard alkali (sodium hydroxide): The aim of the investigation is to determine the relative atomic mass of magnesium by back titration, and therefore, this is the only varied factor in this experiment. For our experiments to be accurate, we expect all results to be concordant, i.e. very similar, within a +- 0.1cm3 range. Results beyond or below this would be considered anomalous, and therefore will be ignored. Sources of Error The magnesium may not be clean. It may in parts, potentially be magnesium oxide, and also, magnesium does have a tendency of tarnishing. To prevent this, we could use emery cloth, and wipe the magnesium thoroughly. The required mass of magnesium needed is 0.3 grams. Weighing this out by trial and error would take us too much time, not to mention how inaccurate it is. So, to overcome this problem, simple algebra is used. We would take 1m of magnesium, weigh this out (assume this value is K), and substitute this into a simple equation. ...read more.


sodium hydroxide solution Pipette - unknown hydrochloric acid solution Burette Rough 1 2 3 Final vol. (cm3) 22.1 46.3 24.3 48.5 Initial vol. (cm3) 0 22.1 0 24.3 Titre (cm3) 22.1 24.2 24.3 24.2 Average tire (cm3) 24.2 Hence 24.2cm3 of standard 0.1M sodium hydroxide solution reacted completely with 25.cm3 of unknown hydrochloric acid solution. Analysis The reactions that were undergone during the reaction were between magnesium with the hydrochloric acid, and the sodium hydroxide with the magnesium chloride solution. The equations (both word and symbol) are shown below: Magnesium + Hydrochloric acid --> Magnesium Chloride + Hydrogen Mg + 2HCl --> MgCl2 + H2 From our results, we are now able to calculate the number of moles of excess acid in 250cm3 of the solution. To do this, we need to be able to calculate the number of moles in sodium hydroxide, using the following equation: Number of moles = volume (in dm3) x molarity Substituting the values gives us: Number of moles = (25 / 1000) x 0.1 = 2.5 x 10-3 moles Therefore, for calculating the number of moles in excess hydrochloric acid, we multiply our answer (number of moles in NaOH) by 10. This gives us 0.025 moles. ...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 the relative atomic mass of magnesium.

    Firstly I would use a gas syringe to increase the accuracy of the readings. I would also try and do something to stop the gas escaping before the bung was securely fixed. This may have been something to do with the errors.

  2. ‘The Relative Strength of an Unknown Acid’.

    Sodium hydroxide should be added until the solution has completely disappeared even after swirling for ten seconds. This is the end point and the reading of the burette should be recorded to the nearest 0.05cm3. White paper placed behind the burette can help to read the result on the burette.

  1. Determination of the relative atomic mass of lithium.

    I always wore safety glasses and a lab coat. Some measurements were limited in their accuracy due to the apparatus used like the measurement of the collected hydrogen in the measuring cylinder, which was measured to the nearest 2cm3. But however careful and accurate one is, there are always factors

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

    + 21.00 + 20.50 3 = 21.58 cm3 Average Titre at 70oc = 21.10 + 20.00 + 21.00 3 = 20.70 cm3 Experiment Five - How much Iron (II) can be extracted from 15 grams of Spinach Oleracea when boiled in Sulphuric Acid (aq)

  1. Titrating Sodium hydroxide with an unknown molarity, against hydrochloric acid to find its' molarity.

    Using the filter funnel and a clean, dry 100 cm� beaker, pour some sulphuric acid into the burette until it is nearly 0 on the scale. Remove the filter funnel after use (ensures 1 from Hazcards #61 2 from Hazcards #98 that no extra liquid from the funnel is

  2. The Determination of an Equilibrium Constant.

    Titrate this mixture with 0.20 mol dm-3 aqueous sodium hydroxide using phenolphthalein as an indicator. * Repeat each titration until concordant results are obtained. * Record all results in an appropriate format. Results: RUN 1 Solution in flask Equilibrium mixture Solution in burette Sodium hydroxide 0.2mol/dm-3 Indicator Phenolphthalein Experiment 1

  1. Titration with a primary standard.

    mol base = MbaseVbase mol base = mol acid x (1 mol base) (1 mol acid) MolarMass Acid = grams acid moles acid The molar mass of solid acid if 1.100 g of acid is neutralized by 26.10 mL of 0.2100 M NaOH.

  2. Determination of the relative atomic mass of lithium.

    So now I can make an average and I can conclude that the result is accurate. The balanced equation I will be using for this experiment is: LiOH(aq) + HCL(aq) LiO(aq) + H2O(l) So to calculate the number of moles of HCL used in titration I will use this equation

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