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Investigation into the effect of concentration on the rate of reactions.

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Introduction

Investigation into the effect of concentration on the rate of reactions. Aim To investigate the effect of changing concentration of hydrochloric acid on the reaction between hydrochloric acid and sodium thiosulphate. The collision theory states that when reacting particles collide with each other a reaction occurs, if there is sufficient energy to react. The three ways of measuring the speed of a chemical reaction are: 1. Measuring the volume of gas production. 2. Measuring the loss of mass. 3. Timing the formation of precipitate. The four factors that change the rate of a chemical reaction are temperature, Concentration, surface area and Catalysts. The higher temperature gives particles more energy so there are more collisions. If the concentration is higher there are more particles, which means there are more collisions. A big surface area means more a greater area for contact and increases the amount of collisions. ...read more.

Middle

Another way is to measure the pH because it will increase or decrease as the reaction takes place. I predict that as the concentration decreases the longer it will take for the reaction to be completed. Apparatus: 2x clonical flasks 1x beaker 5x 25cm3 Sodium thiosulphate 5x 25,20,10,15,5cm3 Hydrochloric acid 5x20,15,10,5,0cm3 water 1x syringe 1xpaper with cross. Method To start off with I will take 25cm3 of thiosulphate and 25cm3 of hydrochloric acid. I will draw a cross on a piece of paper and place it under the beaker. Then I will put the liquids together. I will set the timer and watch the cross until I can no longer see it and at that time I will stop the timer. I will take 5 readings in my experiment recording the concentration of hydrochloric acid and the length of time taken for the precipitate to form. ...read more.

Conclusion

Conclusion I have reached the conclusion that there is a connection between the concentration of hydrochloric acid and the resulting reaction rate. They have a negative relationship. The stronger the concentration the less time taken for the precipitate to form. The reaction rate changes because the higher concentration means more molecules and therefore more collisions, which results in a faster reaction. That rate varies because the concentration affects how fast or slow a reaction takes place. Evaluating The method that I used gave accurate results but I would suggest one change. This would be to use the pH method instead. I think that it may have give more accurate results. All of the factors were properly controlled within the method and I had a stable amount of evidence to meet a firm conclusion. Other experiments I could have done might have been measuring the volume of gas production or measuring the loss of mass. ...read more.

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