the disappearing cross
The task I have been asked to investigate what happens to the reaction between sodium thyosulphate and hydrochloric acid when the solution has been progressively diluted and thus the concentration progressively reduced. The investigation The factor I have decided to investigate in this investigation is what happens to the rate of reaction when the concentration of sodium thyosulphate and hydrochloric acid is progressively reduced. Background The knowledge I already possess which may be helpful is that of previous investigations. The reason the rate of reaction changes when the solution is less concentrated is because the particles are more dispersed and with more water molecules in the way. This makes collisions more difficult. Also, the lower the temperature the slower the molecules are moving so that the chance of successful collisions, a collision with enough kinetic energy to cause a reaction, is greatly reduced. Variables Following is a list of variables in this experiment: 1. Size of conical flask, 2. Delay between adding hydrochloric acid and pressing ‘start’ on stopwatch, 3. Small differences in the amounts of chemicals added, 4. Delay between ‘watcher’ saying stop and pressing ‘stop’ on the stopwatch, 5.