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

Determination of Total Hardness in Water by EDTA Titration

Extracts from this document...


Principles of Environmental Chemistry Experiment 3: Determination of Total Hardness in Water by EDTA Titration Introduction Hardness of water is caused by divalent and multivalent metal that mainly came from contacting with the soil and rock formations. Hardness values are normally expressed in an equivalent amount of CaCO3 in mgl-1. If the hardness of water is smaller than 75mg/l, then it is described as soft water. EDTA can form very stable complex with metal ions (e.g. Mg2+ & Ca2+). The equation: M2+ + Na2H2EDTA � MEDTA2- + 2H+ + 2Na+ In this practical, EDTA (i.e. ethylene diamine tetraacetic acid) is used to determine the hardness of a water sample. EDTA can form very stable complex with metal ions (e.g. Mg2+ & Ca2+) i.e. M2+ + Na2H2EDTA � MEDTA2- + 2H+ + 2Na+ EDTA is added from a burette to the hard water sample and form (MEBT)- complex. At the equivalence point, EDTA removes the metal ion from the (MEBT)- by forming the more stable(MEBTA)-2 complex and free EBT- molecule that is blue in color. ...read more.


/ 3 = 10.40ml Determination of hardness of an unknown water sample (25-ml was used) Trail 1 2 3 Initial Reading 0.00 19.50 10.60 Final Reading 19.50 39.00 30.50 Volume of EDTA used (ml) 19.50 19.5 19.90 Average volume of EDTA used = (19.5+19.5+19.9) / 3 = 19.63ml Data treatment and Questions: Standardization of EDTA Solution Ca2+(aq) + EDTA4-(aq) ? [CaEDTA]2-(aq) Molarity of standard calcium chloride = 0.008 M Volume of standard calcium chloride used = 25 ml No. of moles of standard calcium chloride in 25 ml = 0.008 X 0.025 = 2 x 10-4 mole From the equation above, mole ratio of EDTA: calcium chloride = 1: 1 No. of moles of EDTA used = 2 x 10-4 moles Volume of EDTA solution used= 39.07/ 1000 = 0.03907 dm3 The molarity of EDTA solution = 2 x 10-4 / 0.03907 dm3 = Determination of hardness of a tap water sample: Molarity of EDTA solution = 0.00512M Volume of EDTA solution used= 10.40ml = 10.40/1000 dm3 = 0.0104 dm3 No. ...read more.


It is because EDTA solution made by the latter method is not stable, it is hygroscopic hence it cannot be a primary standard solution. We have to standardize it by calcium chloride solution. On the other hand, calcium chloride solution is a bit unstable indeed, hence the way to produce calcium chloride solution would be from calcium carbonate, which is the "real" primary standard as it is stable enough, in order to produce calcium chloride by reaction. At the second titration, which is EDTA being titrated over tap water, the titrant volume of EDTA is recommended to over 10ml at least. The larger the volume used, the more accurate the result. As error would be minimized due to the following equation: Use the burette with a narrower meniscus to decrease the observation error. The larger the sample size, the smaller the relative error. Precaution: 1. While adding indicator, do not put too much amount of indicator into the conical flask, otherwise the too deep colour affects the judgement of end-points of the titration. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Inorganic 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 AS and A Level Inorganic Chemistry essays

  1. Peer reviewed

    Determining the concentration of acid in a given solution

    5 star(s)

    was much higher than it actually was as only a small amount was needed to create the colour change. Precision Uncertainties 7, 8 Apparatus Uncertainty Percentage uncertainty % How could this be improved? Burette 0.05cm3 (0.05 / 24.6) x 100 =0.20% There is always an error whilst using a burette

  2. Peer reviewed

    Deducing the quantity of acid in a solution

    5 star(s)

    = C (concentration) x V (volume) Volume of the flask: 25cm3 = 25 x 10-03 dm3 n = 25 x 10-03 x 0.1 M n = 2.5 x 10-03 moles of Na2CO3 Step 6: Ratio of the reactants. As we saw in the reaction, the ratio of reactant is 1:1.

  1. effects Concentration and Temperature on the Rate of Reaction

    of data - as 1/temperature is increased, log to the base e of reaction rate decreases. To find the gradient of a straight line, you use the following equation: (7) Gradient = Change in y value Change in x value For my graph, I worked out the gradient as follows:

  2. ethanedioate complex of iron

    The crystals were separate by filtration using a sintered-glass funnel. Then it were washed twice with a mixture of equal volumes of ethanol and water, and followed by twice with acetone. The solid was allowed to air dry by suction.

  1. Lab report Determination of Enthalpy Change of Neutralization

    On top of that, we had used the measuring cylinder to measure 25 cm3 of acid or alkali which is less precise than using the pipette to get 25cm3 of acid or alkali. As the volume we got was not equal to exact 25 cm3 of acid or alkali, the

  2. Determination of DO & BOD in a water sample

    2.> In the experiment, DO0 is 7.90 mgdm-3. This value is higher than the minimum requirement for fishes (4-6 mgdm-3). As the water used is aquarium water, oxygen is always replenished by air pump and the DO is enough for fishes.

  1. Scientific Practical Techniques

    not be seen through nicked eyes, haemocytometer a device originally used to count blood cells it is now used to count cells and many types of microscopic particles, micropipette a pipette designed for the measurement of very small volumes mostly used in hospital and also a growing yeast culture placed in a bakers at 30 degree temperature.


    Assume that the specific heat capacity of the solution is the same as water, 4.18 KJKg-1K- . Ans: ? H for HCL: ?H = MC? T Volume is 71cm3 = 71/1000 = 0.071 dm3 Temperature = recorded from the graph (final - initial). ?H = (volume of NaOH + HCl)

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