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Investigate the effect of sodium carbonate on hard water.

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CHEMISTRY GCSE COURSEWORK: PLANNING AIM: To investigate the effect of sodium carbonate on hard water. METHOD: I am going to use titration in this experiment. To do this, I will use soap solution in a burette, I will use a pipette and a filler to get 25.0cm3 of hard water (the laboratory tap water). Then I will weigh out and add sodium carbonate (starting at a control of 0.000g and not going any higher than 6.000g) to the water and dissolve it. After doing this I will add soap solution (0.5cm3) to the solution, and shake it for 10 seconds. We will time this using a stopwatch/stop clock. We will then see if a permanent lather forms (a permanent lather is a lather that lasts for at least 10 seconds), which is also timed using a stopwatch/stop clock. I will continue to add soap solution until a lather forms. This will tell me if the sodium carbonate has made the water softer of harder. If a lather forms after only using 1cm3 - 3cm3, then it has been softened by the sodium carbonate, because all the calcium ions have been used up quickly; however if it takes over 6cm3 of soap solution to form a lather, then the sodium carbonate hasn't really softened the water and more sodium carbonate is needed. ...read more.


sodium carbonate to use up all the calcium ions and soften the water that no extra soap solution will actually be needed. I think that the graph is going to look like this because, at first when the sodium carbonate is added, there will be a large decrease in the volume of soap needed, however eventually, after a certain amount of sodium carbonate added, there will hardly be any soap solution needed. From then on, the volume of soap needed will be the same or there will only be a small decrease, so therefore the curve will start to slow down and instead of the volume of soap needed, decreasing rapidly, the volume of soap needed, will decrease but not so quickly. In the experiment, we are going to range the mass of sodium carbonate. However we are not going to use more than 6g of sodium chloride. I am going to use 8 different masses (0.0g, 0.5g, 1.0g, 2.0g, 3.0g, 4.0g, 5.0g, 6.0g).However, for each mass, 1 result is definitely not enough as that 1 result could be a rogue result. So I am going to get 3 results for each mass, so I can find out if one of the results was wrong. ...read more.


7 very hard Scottish Natural Mineral Water 5 hard Lab Tap Water + Calcium Hydrogen Carbonate 16 extremely hard Lab Tap Water + 0.5g of Sodium Carbonate 4 medium Lab Tap Water + 2.0g of Sodium Carbonate 2 very soft From these results, we can tell that the more calcium ions there are in the water the harder the water is and therefore more soap solution (which contains stearate) is needed to get rid of all the calcium ions. In the experiment we are about to do, we know that we need more soap solution to get rid of calcium ions, but we also have sodium carbonate (which contains carbonate ions) which also helps to use up calcium ions. As shown in the results, we can see that using sodium carbonate definitely softens the water. In the experiment that we are about to do, instead of only using two masses of sodium carbonate with water, we are going to use more masses (8 to be precise), so that we get more accurate and reliable results. So, we know from previous experiments that the more sodium carbonate added, the less stearate/soap solution need to soften the water, and the more sodium carbonate added, the softer the solution. WILLIAM KEISNER 4S 1 ...read more.

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