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Investigate the effect of solution concentration on osmosis

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Investigate the effect of concentration on the rate of reaction between sodium thiosulphate and hydrochloric acid. Aim The aim of my investigation is to see how the concentration of sodium thiosulphate affects the rate at which a reaction occurs between hydrochloric acid and sodium thiosulphate. Introduction To investigate the effect of concentration on the rate of reaction between sodium thiosulphate and hydrochloric acid, I will conduct an experiment. When thiosulphate reacts with hydrochloric acid, a cloudy yellow precipitate is formed. The chemical equation for this is as follows: Na2S2O3 (aq) + 2HCl (aq) 2NaCl (aq) + SO2 (g)+ S (s)+ H2O (aq) I will use the above reaction to help me measure the rate of reaction. I shall place a laminated cross on paper underneath the conical flask and I will use a stopwatch to help me measure the time it takes for the cross to become completely obstructed from view by the cloudy precipitate. There are several factors that will affect the rate of reaction and therefore final outcome of this experiment. They are as follows: but first let me explain the collision theory as this will help to explain the factors that affect the rate of reaction. The Collision Theory If you have a situation involving two species, they only way then can react with each other, are if they come into contact with each other. ...read more.


Pressure If one or more of the reactants are gaseous, (which neither of mine aren't), then increasing pressure will effectively increase the concentration of the reactant molecules and therefore speed up the reaction. Catalyst The word catalyst means an added substance, in contact with the reactants, that speeds up the rate of reaction without itself being chemically changed in the end. A catalyst works by lowering the activation energy needed to start the reaction. Here are two graphs explaining the use of a catalyst on activation energy in an EXOTHERMIC reaction and an ENDOTHERMIC reaction. They are widely used in different reactions in industries to increae the speed of reaction and therefore lower the cost of producing the reactions as the high temperatures and pressures needed, are decreased. To ensure a fairer test I will keep the following possible variables, constant: The volume of hydrochloric acid will always be 5.00cm�. I will try and keep the temperature of the substances the same each time (room temperature). I will try my hardest to stop the watch at the correct time, but due to unavoidable human error, I can not ensure 100% accuracy every time. Prediction I predict that the higher the concentration of sodium thiosulphate, the quicker time it will take to react with the hydrochloric acid. ...read more.


I know that if two solutions are reacting, and one solution is diluted with water, then the reaction will take longer as there are less reactive atoms present to collide and cause a reaction. Evaluation I am very pleased with my experiment's final results as they match my prediction. The results I got fitted in the line of best fit of my graph so again, I am pleased with my experiment. If I were to do my experiment again, there are a few things I would consider. Due to a factor of human error, I cannot be exactly accurate when timing how long it takes for the cross to become invisible, or when measuring solutions. So next time, if I do this experiment again, I would use a burette to measure the solution as this instrument is a lot more accurate then the measuring cylinder. Also I would use a light beam to more accurately decide when the cloudy precipitate has completely covered the cross. To make the results even more accurate I would have used a wider range of concentrated solutions of thiosulphate. E.g. instead of only 0.01 mols/dm�, 0.03 mols/dm�, 0.06 mols/dm�, 0.09 mols/dm�, 0.12 mols/dm�, 0.15 mols/dm�, I could use from 0.01 mols/dm�, going up by .01 each time until 0.15 mols/dm�. This would ultimately give me a more accurate final result. ?? ?? ?? ?? Leon Simmons - 0185 Centre Number - 53617 ...read more.

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