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Science Coursework

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Science Coursework Sumaiya Vora 10z Title Investigation on how the rate of reaction between sodium Thiosulphate and hydrochloric acid is affected when the concentrations of sodium Thiosulphate are changed. Aim: ? I am going to investigate how the rate of reaction is affected when the concentration of sodium Thiosulphate is changed. The experiment will be done by mixing the various concentrations of sodium Thiosulphate with hydrochloric acid and by timing how long it takes for a cross to disappear. This will be able to be done because one of the products of the reaction is sulphur, which is an insoluble substance. As it forms the mixture becomes cloudy and the cross will eventually won't be seen. Word and Symbol Equation Sodium + Hydrochloric Sodium+ Sulphur+ water + sulphur Thiosulphate Acid Chloride dioxide (Aq) (g) (L) (s) Na2S202 + 2HCL 2NaCl+S+H2O+SO2 Background Information ? Sodium Thiosulphate Sodium Thiosulphate is a chemical used in photography. If a clear solution of sodium Thiosulphate was mixed with hydrochloric acid a reaction occurs and a creamy yellow precipitate is produced which is sulphur. Along with sulphur, sulphur dioxide, water and sodium chloride are formed. This precipitate does not form immediately, but it begins to appear after a short while, this therefore turns the mixture cloudy Rates of Reaction Rates of reactions can go at all different sort of rates. One of the slowest reactions is iron rusting. Other slow reactions are chemical weathering like acid rain damage to limestone buildings and statues. A metal like magnesium reacting with acids to produce bubbles is a normal speed reaction. A really fast reaction is an explosion such as firework. The rate of reaction depends on four main aspects. They are 1. Temperature The temperature affects the rate of reaction because it makes the rate of reaction time slow down or get quicker. If the temperature has been increased then the reaction is quicker and the solution becomes cloudy quicker. If the temperature has been decreased then the reaction is slower. ...read more.


(if anyone were running then things may get split and may hurt themselves especially with glassware and other chemicals) 6. do not alter or disturbs anyone else's work( it will cause there data to be wrong and it is not fair. Safety needed in this experiment 1. follow all general safety rules (it is always need dangerous or not. It I still needed. 2. Make sure people who have asthma have their asthma pump(they could have an asthma attack as sulphur dioxide is being given off during this experiment) 3. Close all chemical bottles (to avoid spillage) 4. Make sure all glassware and equipment is on the middle of the table. (if it was on the edge then the probability of it falling is much higher. 5. be careful with using the acid.(acid is corrosive-Could Cause Burns) 6. Do the experiment in an well-ventilated room. (sulphur dioxide is being given off. Results Volume of sodium Thiosulphate (Cm3) Volume of water (cm3) Concentration (g/L) Time 1 (S) Time 2 (S) Time 3 (S) Average time for cross to disappear (S) Rate of reaction (S 1) Volume of acid HCl (Cm3) Time taken for the cross to Disappear. 50.0 0.0 50.0 33. 49 42 42 0.0238 5.0 40.0 10.0 40.0 43. 93. 47. 61 0.0164 5.0 30.0 20.0 30.0 67 75 75 72 0.0139 5.0 20.0 30.0 20.0 115 164 129 136 0.0074 5.0 10.0 40.0 10.0 208 199 250 219 0.0046 5.0 Results analysis I found out using the table the pattern and the rate of reaction. The pattern in the results how is that thee concentration of sodium Thiosulphate affects the time taken for the cross to disappear. As you go down the results table, the times gets slower for the solution to get cloudy there was an reading which is not on the pattern trend. Which is on the time 2 column and the 40.0cm3 row. ...read more.


With Graph B 3 data points were on the best fit line but two at 20.0g/L and 40.0g/L were lower than expected. These two data points seem to be my anomalous results. Percentage Error for 20g/L =0.0095-0.0075 X100 =21% 0.0095 percentage error for 40g/L =0.0190-0.0165 X100 =13% 0.0190 For all the other data points 10.0g/L and 20.0g/L and 30.0g/L the percentage error was about 0%. These data points were on or very close to the line of best fit in graph B. The reason for the anomalies data for 20.0g/L and 40.0g/L could be because I made the concentration of sodium Thiosulphate to dilute than it should be. Another reason may be because I did not time the reaction properly and I was late in stopping the timer when observing the black cross. The reason is more likely as I was very careful when I made the various concentrations of sodium Thiosulphate from the stock solution given to us. I also did have problems deciding when to stop the time because sometimes I was thinking to myself has the cross disappeared. This bit of the experiment was flawed and not very precise despite my attempts. One way round this would have been to increase e the reliability of data but repeating the experiment more than three times so around eight or nine times for each concentration. The only problem is I would have taken more time then we had available. Overall my data is strong evidence that supports my prediction. Self Evaluation I think and I am sure that I did what was needed to do in the experiment. I had an equal part in it. I had listened quite well to instructions also I had an a good plan and table drawn up to help me write in the data. This made the experiment went well. Sumaiya Vora 10z Science coursework Page 17 of 17 ...read more.

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