The Effect of Sodium Thosulphate Solution on the Rate of Its Reaction with Hydrochloric Acid

The Effect of Sodium Thosulphate Solution on the Rate of Its Reaction with Hydrochloric Acid
Aim To find out how the concentration of sodium thiosulphate solution affects the rate of its reaction with hydrochloric acid. Prediction I predict that the higher the concentration of Sodium Thiosulphate solution the faster it will react with the hydrochloric acid. Firstly for a reaction to take place the particles must collide and secondly collide with enough energy to break and make new bonds. When the sodium thiosulphate is concentrated there are more particles in a given volume, therefore there is a greater chance of the particles successfully colliding and reacting with the hydrochloric acid. The more collisions between particles in a given time, the faster the reaction will take place.Sodium Thiosulphate Sodium Chloride + Sulphur dioxide + Hydrochloric Acid + Sulphur + Water Symbol Equation [image]Naâ??Sâ??Oâ?ƒ + 2HCl 2NaCl + SOâ?? + S + Hâ??O The products of this equation are sodium chloride, commonly known as salt, sulphur dioxide, which is a highly toxic gas, water and sulphur. The sulphur is a precipitate and this is what turns the solution cloudy. Method To find a suitable method I firstly looked back at the previous work I had done in class, to see if there were any similar experiments that could be used as pilot tests. I found that I had done a similar experiment using the same reactants, but instead of looking at the effects of concentration, I had looked at temperature. The amounts used 50cm³ Sodium Thiosulphate and 5cm³ Hydrochloric acid. The experiment had worked well and I had drawn good results so these amounts were suitable. Also I looked in a chemistry book by Hunt and Sykes book which happened to have the same experiment in. They to had used these amounts and this confirmed the quantities that I thought would be appropriate to use, although I decided to go up in fives instead of tens. This gave me good idea of what to aim for in my experiment, so I would know if there were any anomalies throughout the test. The table goes as follows: [image] I started by arranging all the equipment on my desk. I kept all the equipment for hydrochloric acid on one side of the conical flask and the water and the Sodium Thiosulphate Solution on the other side. I did this so there would be no contamination. It did not matter that the Sodium Thiosulphate Solution and the water were together, as they were mixed together to achieve the different concentrations of Sodium Thiosulphate Solution. I did this by starting at 50cm³ of Sodium Thiosulphate Solution, then 45cm³ and 5cm³ of water. I went down in fives to 5cm³ of Sodium Thiosulphate Solution and 45cm³ of water. (There was no need to do all water as this would have taken to long). I measured the amounts needed very accurately, using pipettes and appropriate sized measuring cylinders. When I had got the Sodium Thiosulphate Solution and water to equal 50cm³, I measured the temperature. If it was the correct temperature then I poured into the conical flask and then added the 5cm³ Hydrochloric acid. I swirled the contents of the conical flask while my partner started the stop clock. If the temperature was too hot then I ran the conical flask under a cold tap, (being careful not to let any water inside, as this would make the test unfair). If it was too cold then we heated it up placing it over a Bunsen burner for a few seconds. I watched over the top of the conical flask until I could not see the cross anymore and then stopped the clock. I then recorded the time and moved on to the next concentration. Diagrams [image] Apparatus The apparatus I used for this experiment was: Â? 250cm³ beaker to keep the main supply of hydrochloric acid in Â? 250cm³ beaker for the Sodium Thiosulphate Solution Â? 50 cm³ measuring cylinder for measuring the water accurately Â? 50 cm³ measuring cylinder for measuring the Sodium Thiosulphate Solution Â? 10cm³ measuring cylinder for measuring the hydrochloric acid to be measured accurately in. Â? Pipettes (´3 one for each liquid) to measure the liquids accurately. Â? Thermometer to measure the temperature if the water and Sodium Thiosulphate Solution before being added to the Hydrochloric acid Â? Cross to time how long it took for it to disappear Â? Conical flask for the reaction to take place Â? Stop clock measuring to the nearest second to time the reaction Safety Safety was very important in this experiment, as I was dealing with lots of different substances that can be dangerous. [image][image] These are the symbols for Sulphur dioxide. This is a gas, which is toxic and corrosive, so I opened the windows and after the experiment the conical flasks were placed in the fume cupboard. Toxic means that it can cause death. It may have effects if swallowed, breathed in, or absorbed through the skin. Corrosive means that it attacks and destroys living tissues, including eyes and skin. Also, for safety I wore goggles to protect my eyes from the Sulphur dioxide, when we had to look over the conical flask to see when the cross had disappeared. (When looking at the cross I did not go to near so no Sulphur dioxide was breathed in). [image] I was careful of the Hydrochloric acid, because it is corrosive and can cause burns. Also, for safety I wore goggles to protect my eyes from any splashes that could have accrued. [image] The sulphur is highly flammable so I kept it away from the Bunsen burner used to heat the concentrations of the Sodium Thiosulphate Solution. The sodium chloride was only minimally harmful if ingested in large quantities. I tied my hair back, placed my stool under the bench and remained standing throughout the test in case of spillages. Also to help prevent spillages I placed the experiment in the middle of the table Finally, I made sure I could hear any instructions given by remaining fairly quiet and not shouting. Fair test [image] To make this experiment fair it was important to keep the key factors controlled and to only change one variable, in this case the concentration. I made sure that I measured all the amounts carefully so that there were no anomalies in the results. Also I used the same sized conical flasks so that the distance to see the cross was the same. (If the conical flask was smaller then the height of the liquid would be higher, therefore more to see the cross through. I decided to go up in intervals of 5cm³ so that a more accurate graph could be drawn. I repeated each concentration 3 times, as this is more accurate when an average is taken. It was important to keep the temperature constant throughout the experiment, as an increase or decrease would have affected the rate of the reaction. As the temperature increases the particles have more kinetic energy and therefore have more energy to break and make bonds. This increases the chances of successful collisions, because the particles are more likely to come into contact and collide with enough energy to make new bonds. When measuring the Hydrochloric acid in the small measuring cylinder I was careful to measure to the bottom of the meniscus. This effect occurs because of surface tension. Because the attraction between the SodiumThiosulphate Solution particles and the glass is greater than the surface tension in the liquid it causes it to curve upwards at the edges. [image] To keep the test fair it was important to use the same source of Hydrochloric acid and Sodium Thiosulphate Solution because it is possible that they could change slightly and this could slow down or speed up the test. Also when I added the two liquids I swirled them. I made sure I did this to all the tests. I did this because in the concentrated Sodium Thiosulphate Solution the water would settle at the top if left for a while. I made sure that I used the same cross while doing the test as, if the cross got thicker or darker then it would take longer to not be able to see it. Also I made sure I looked at the cross each time, because people have different eyesight and what one person thinks has disappeared might be just visible to someone else. When timing the experiment I only timed it to the nearest second. Although this does not seem very accurate, the test, overall, was not that exact as it was only done by sight. Therefore timing it to he nearest second was as accurate as it needed to be. It was important to make sure that the equipment that I was using was clean before I used them. Also I made sure that I washed them out well after each test to stop any contamination. Volume of sodium thiosulphate (cm³) Volume of water (cm³) Total Volume (cm³) Volume of Hydrochloric Acid (cm³) Temperature (Â?C) Time (nearest second) Rate of Reaction 1st 2nd 3rd 1st 2nd 3rd Average 1/t (/s) (5 d.p.) 5 45 50 5 22 21 22 1456 1501 1476 1478 0.00068 10 40 50 5 22 22 23 910 876 901 896 0.00112 15 35 50 5 21 22 23 545 545 531 540 0.00185 20 30 50 5 22 23 21 311 310 283 301 0.00332 25 25 50 5 21 21 22 195 190 197 194 0.00515 30 20 50 5 21 21 21 94 112 100 102 0.00980 35 15 50 5 21 21 20 78 80 82 80 0.01250 40 10 50 5 21 22 22 60 65 59 61 0.01630 45 5 50 5 21 22 21 55 57 58 57 0.01765 50 0 50 5 22 22 21 46 47 45 46 0.02174 Results Conclusion This experiment has proved my prediction correct. I predicted that ?the higher the concentration of Sodium thiosulphate solution the faster it will react with the hydrochloric acid." This happened because, firstly for a reaction to take place the particles must collide and secondly collide with enough energy to break and make new bonds. When the sodium thiosulphate solution was concentrated, there were more particles in a given volume, therefore there was a greater chance of the particles successfully colliding and reacting with the hydrochloric acid. The more collisions between particles in a given time, the faster the reaction took place. My first graph shows that my prediction was correct because the result for 10cm³ was 775 seconds and my result for 20cm³ of was 250 seconds. This shows that the more Sodium Thiosulphate solution the less time it took and the quicker the reaction took place. The results were quite close to the results in the book that I was aiming for. The reason that they were a bit different was that a slightly stronger acid was used (0.15) whereas I used a more dilute one (0.1). This meant that my reaction times were slightly slower for my results. From the results I drew two graphs; one to show the relationship between the concentration and time and one to show the rate of reaction. The first graph was a constant/x² curve. The curve gets shallower and shallower but never touches the zero line. This is because the more dilute the acid becomes the longer it will take for the Sodium Thiosulphate Solution to react with the Hydrochloric acid. It showed that the concentration of the Sodium Thiosulphate Solution (when reacted with Hydrochloric acid) is proportional to the inverse square. For my second graph I drew a graph to show the rate of reaction. I drew a line of best fit. This shows that if the concentration of Sodium Thiosulphate is doubled then so is the rate of reaction and therefore was directly proportional. To find the rate of reaction from the averages I had found in my result table, I used 1/average time the reaction took. I then worked out an equation for the line of best fit. I worked out the rate of reaction for 50cm³ of Sodium Thiosulphate Solution when reacted with Hydrochloric acid by using the equation y = 0.00036×. I substituted the x for the 50 and I got the answer 0.018. I then looked at the graph and this result matched the line of best fit. I then tried it again with 25 cm³ Sodium Thiosulphate Solution and I got the answer 0.009. Again I looked at the line of best fit and it was correct. I can estimate further answers that I have not had time to try, by using this equation. For example if I wanted to know what the rate of reaction would be for 27cm³ of Sodium Thiosulphate I would use the equation, substituting x for 27 I would get the answer 0.00972. This result fits on to the line of best fit. Evaluation I think that this experiment was a success as the results proved my prediction correct. I think that method that I planned worked well and the results for my first graph were accurate. I repeated each concentration three times and I think this was enough to get accurate results from. Also I used a range of concentrations. I went up in intervals of five and this would have also give more accurate results than if I had gone up in tens. Therefore I think that these results are good enough to support a firm conclusion. The apparatus I used was very accurate. I used measuring cylinders instead of beakers to measure the hydrochloric acid, the Sodium Thiosulphate Solution and the water. Also I used pipettes instead of just pouring, for even more accuracy. There were one or two slight anomalies. The greatest ones were 5cm³ of Sodium Thiosulphate Solution and 15cm³ of Sodium Thiosulphate Solution. The reasons that these occurred could be that I had to do the experiment on two different days. The temperatures could have been slightly different and although I measured them, even a slight difference could have changed the results. Another reason is that a different source of acid was used. If there was a slight difference in the concentration of this it could have speeded up or slowed down the reaction time. I think that the results were not as accurate as they could have been as they were on measured by sight. If I did the experiment again and I had the equipment available to me then I would use light sensors, which were connected to computers, which can accurately measure when the solution goes cloudy. [image] [image] Another way off measuring them would be to measure the gas given off from the test. This would not have been as accurate, but I could compare the results to see if there were any similarities. If I did the test again I think that I would do even more repeats, for each concentration. This would make the results more reliable. I might change the concentration of the Hydrochloric acid and react it with Sodium Thiosulphate Solution. It would be good to see if the results were the same. Also I would try the same experiment but at different temperatures. I would try the same concentrations at a higher temperature and add this information on to the graph that I had already drawn to see how much the reactions are speeded up by. Finally I would investigate by using different reactants to see how this effected the rate of reaction.

The Effect of Sodium Thosulphate Solution on the Rate of Its Reaction with Hydrochloric Acid 7 of 10 on the basis of 2114 Review.