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Chemistry coursework. Rates of reaction

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How The Concentration Of The Sodium Thiosulphate Affects The Rate Of Reaction Of Hydrochloric Acid and Sodium Thiosulphate THE PROBLEM What Do You Want To Find Out? I want to find out if as the concentration of sodium thiosulphate decreases the rate of reaction i.e. the rate of reaction is directly proportional to the concentration of the sodium thiosulphate. BACKGROUND KNOWLEDGE What Scientific Knowledge Do You Have Which Might Be Useful In Planning Your Investigation? We have scientific knowledge from preliminary experiment of hydrochloric acid and sodium thiosulphate. Na S 0 + 2HCL 2NaCl + H O + SO + S � � � (aq) (aq) (aq) � (�) � (aq) (s) When 10cm� of 1M HCL was added to 50cm� of Na S O (40g/dm�) after about 60 � � � seconds the sodium thiosulpahte clouded over and prevented us from seeing the x placed on a piece of paper beneath the conical flask. The reaction was exothermic and the bottom of the flask became hot. PREDICTIONS From What You Already Know What Do You Think Will Happen? How Do You Think This Will Happen? ...read more.


From this I shall work out the rate (1/time) of reaction of each concentration. I will then draw a line graph with concentration on the x axis and average rate on the y axis. I will draw a line of best fit and find the mathematical relationships between the concentration and rate. Concentration of Sodium Thiosulphate (g/dm�) Time 1 for Na S O � � � to cloud over (S) Time 2 for Na S O � � � to cloud over (S) Average Time (S) Average Rate (1/time) (S) 40 32 24 16 8 29 38 47 69 169 28 35 46 70 159 28.5 36.5 46.5 69.5 164 0.04 0.03 0.02 0.01 0.006 PRATICAL PROCEDURE Apparatus: Conical Flask Two 50cm�-measuring cylinders Piece of paper with an X on it Stopwatch Chemicals: 50cm� 40g/dm� of Sodium Thiosulphate 10cm� 1M of Hydrochloric Acid Safety: Wear safety glasses Keep apparatus to side of bench Clean spills immediately Diagram: Method: Measure out 50cm� 40g/dm� of Sodium Thiosulphate using a clean and washed measuring cylinder. Place in a conical flask. Measure out 10cm� 1M of Hydrochloric Acid using another clean measuring cylinder. ...read more.


EVALUATING Do You Think Your Method Was The Best Way Of Doing The Investigation? The method I used was a reliable method at this level. It was relatively easy to control the variables and to identify the end part of the reaction. If You Did It Again, What Improvements Would You Make? If I did the experiment again I would make a few improvements: (a) I would use a colorimeter to give an exact measurement of the cloudiness of the solution. (b) We would repeat each experiment more times to ensure it was as reliable as possible but to enable us to do this we would need a lot more time to carry out the investigation. Were There Any Results That Did Not Fit With The Main Pattern? If So, Can You Explain Why? There was one result at 8g/dm� of Sodium Thiosulphate when we repeated it the second time the time was a sufficient amount less than the first time. This could have been because there was a fault in the timing or we possible diluted the solution too much. Do You Think Your Results Are Good Enough To Convince Other People? I believe that these results are accurate enough to convince other science students that my prediction was correct. ...read more.

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