• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14
  15. 15
  16. 16

In this experiment, we aim to investigate the effect of sodium carbonate on hard water.

Extracts from this document...


GCSE CHEMISTRY COURSEWORK: INVESTIGATING HARD WATER 1. PLANNING Aim In this experiment, we aim to investigate the effect of sodium carbonate on hard water. Method Firstly, 25.00cm3 of a sample of water was pipetted into a clean conical flask. The pipette was used because this measures and delivers a very accurate amount of liquid (to the nearest hundredth of a cm3, or 0.01cm3), but care had to taken to make sure it was not held by the bulge, as this could have made the amount inaccurate (as body temperature heats the apparatus up and makes it expand). Also, the pipette is used to avoid spillage, as the thin tube can put the water straight into the appropriate container. Furthermore, a pipette filler was used for safety purposes, because blowing or sucking could get unwanted and potentially dangerous substances into the mouth. 0.500g of sodium carbonate (a white powder) was added to the water, having been carefully weighed on an electronic balance - this was very exact and had a cover to maximise accuracy (it protected the balance from being affected by wind or other particles). The balance measured the mass of the powder to the nearest thousandth of a gram (i.e. 0.001g). Then a burette on a stand was obtained, a considerable amount of soap solution funnelled into it through the top (so the level reached near the top) and 1cm3 of the solution added to the water. The burette (glass tube with measurements marked on the side and a stopcock at the bottom) was used because it very accurately lets out 1cm3 every time. The conical flask was then corked (so no substances were able to escape through the top) and shaken for ten seconds (this timed by a stop-watch). It was observed whether a permanent lather (one that lasted for more than ten seconds - again a stop-watch was used) was created. ...read more.


8. N.S.P. (normal safety precautions) apply. Results Mass of sodium carbonate (g) Volume of soap solution used (cm3) Average (cm3) 0.000 7.00 6.50 7.00 6.83 0.500 6.00 6.00 6.00 6.00 1.000 5.00 5.50 6.00 5.50 1.500 4.50 5.00 4.50 4.67 2.000 4.00 4.50 3.50 4.00 2.500 3.00 4.00 3.00 3.33 3.000 2.50 2.50 2.50 2.50 3.500 2.00 2.50 1.50 2.00 4.000 1.50 2.00 1.50 1.66 4.500 1.50 1.50 1.50 1.50 5.000 1.50 1.50 1.50 1.50 [N.B. For every individual test, 25.00cm3 of water was used.] 3. ANALYSING AND CONSIDERING EVIDENCE Analysis In the experiment, it was seen that the more sodium carbonate was added to the water used, the less soap solution was necessary to produce a lather. This can be best illustrated by a graph of the results (see pg. 12). The graph makes clear some trends in the results obtained. At first, when the mass of sodium carbonate powder is gradually increased (by 0.500g each time), the amount of soap solution needed to make a lather steadily decreases. Then, after 3.000g of powder is used, the graph begins to level off into a plateau, indicating that however much more sodium carbonate one adds, the quantity of the necessary soap to produce a lather will remain the same. This is explained below. Water becomes 'hard' when it is dissolved with calcium (Ca2+) ions (or magnesium, Mg2+, ions). To soften this water, one has to remove these ions. One method of removing the calcium ions is to add sodium carbonate. When the calcium ions (from the water) and the carbonate ions (from the sodium carbonate) react together, calcium carbonate is formed: Ca2+(aq) + CO32-(aq) ( CaCO3(s) And this is the equation with all the ions involved: CaSO4 (aq) + Na2CO3 (aq) ( CaCO3 (s) + Na2SO4 (aq) (calcium sulphate from hard water)(sodium carbonate)(calcium carbonate)(sodium sulphate) So here the sodium 'wins' the sulphate away from the calcium because it is higher in the reactivity series of elements. ...read more.


then should have been, so the water was actually harder than it should have been, and more soap was needed for a lather to appear. Also, the anomalies could have been recorded because a different set of equipment was used for different stages - if, for example, one electronic balance used was slightly inaccurate (because of damage, say) and another was absolutely accurate, then minor differences in exact result trends would be seen, and on the graph these appear as wrong anomalies. This is because, if a inaccurate amount of sodium carbonate was added, then the water would become either softer or harder than expected, and so the amount of soap needed to make a lather would rise or fall accordingly, too. More work could be done to extend this investigation and thus provide more support for the conclusion. Many different samples of water (e.g. distilled, from the laboratory, from students' homes) could be tested by a similar process to the one in this experiment. Same amounts of the types of water could be put into conical flasks (using pipettes) and then the soap solution poured into them via the burette. It would be recorded how many cubic centimetres were needed to produce a lather, as in this coursework experiment. This would show that the calcium ions have the effect of reducing the amount of lather. This is because the distilled water, which is pure H2O, with nothing dissolved in it (including calcium ions), would be proved to be very soft (producing a lather very quickly with the soap solution), whilst another type of water, which has many calcium ions dissolved in it, would be very hard (a lather made only after much soap solution was added). All this information would allow me to confirm my conclusion here that the more sodium carbonate is used and the more calcium ions can be removed by it, the faster a lather will be seen and so the softer the water will be. Jakub Figurski, 4A 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. Marked by a teacher

    chemistry coursework

    4 star(s)

    The reason for this is explained above. I conclude that some of my prediction matched my results. I predicted the greater the volume of potassium iodide in solution, the faster the reaction would take place. The smaller the volume of potassium iodide in solution, the slower the reaction would take place.

  2. An Experiment to Determine the Enthalpy Change for the Decomposition of Calcium Carbonate.

    8469.552 = 169391.04J / 169.39104KJ 0.05 The answer will be negative because it is an exothermic experiment. Answer: �169.4KJ to 3 s.f Enthalpy change for decomposition of calcium carbonate So from the calculation above I can now work out the change in heat produced from calcium carbonate (CaCO3)

  1. The aim of this experiment is to answer the following question: What is the ...

    be a colour change at a different point to when I expect one, so making the amount of indicator constant should eliminate this. :) When moving the sample I take from the reaction vessel to be titrated I will move it quickly as possible so that the temperature will not

  2. Determination of the Heat of Formation of Calcium Carbonate

    Reaction of Calcium Carbonate with Dilute Hydrochloric Acid 1. About 2 - 2.5 g of dry powdered calcium carbonate is weighed out accurately and being put directly into a clean dry plastic cup inside a beaker. 2. About 100 cm3 of the hydrochloric acid is placed in a measuring cylinder.

  1. Heat of Formation of Calcium Carbonate

    (Call this Equation 1) A3. Ca(s) + C(s) + 3/2O2(g) --> CaCO3(s) ___________________________________________________________ Q4. Write an ionic equation for the reaction taken place. (Call this Equation 2) A4. Ca(s) + 2H+(aq.) --> Ca2+(aq.) + H2(g) Q5. Calculate, in each experiment, the heat change in the reaction between the calcium and the acid per gram of calcium.

  2. Analysing Soft Drink

    Colour matching Colour matching is a method relies on a person's eyes to determine the intensity/ the wavelength of light of a coloured solution with the nearest colour from a set of coloured standard solution. This method however is not accurate as human errors can be made because it relies on the judgment of the person's eyes.

  1. AS Chemistry - Investigate the effect of sodium carbonate on hard water

    I predict that the graph will start high showing that a lot of the soap solution would be required to create the unbroken lather on the surface for ten seconds. Then when one gram of sodium carbonate is added, the amount of soap solution required to create a lather will be much less.

  2. the synthesis of azo dyes, aspirin and soap

    The alcoholic oxygen atom has now got a temporary positive charge as it now has three bonds to it in the intermediate at step 2 of the reaction mechanism.

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