Investigating The Rate Of Reaction Between Sodium

Thiosulphate And Hydrochloric Acid Essay, Research Paper

Investigating the rate of reaction between Sodium

Thiosulphate and Hydrochloric Acid Diagram

Aim : We did 4 experiments to find out how

the rate of reaction changes with differing concentrations of Sodium

Thiosulphate, Hydrochloric Acid and water. As an inert and stable liquid, water

was used to alter concentration of Sodium Thiosulphate without changing the end

amount of solution. All the atoms in a water molecule have a full outer shell,

so they would not react with the other chemicals.Equipment ???? Beakers, ??????????????????????? Measuring cylinders Clamp stand and Clamps ??????????????????????? Black paper tube ??????????????????????? Light probe and Blue box ??????????????????????? Datalogger ??????????????????????? Lamp ??????????????????????? Total of 30cm3 H 0,

50cm3 Na S O , 12cm3 HClMethod : We wanted to change the concentration

of Sodium Thiosulphate and Hydrochloric Acid, but without changing the overall

quantities. To do this, the Sodium Thiosulphate and water were mixed at

different ratios, with always a constant amount of acid. The table below shows

the 4 different experiments, and what each solution composed of. The ?Graph?

column relates to the graphs taken from the Datalogger for that experiment,

which are included at the back of this piece. Sodium

Thio-sulphate (cm3) Water

(cm3) Hydrochloric

Acid (cm3) Graph

number 20 0 3 DPPAS_02 15 5 3 DPPAS_03 10 10 3 DPPAS_04 5 15 3 DPPAS_05 ? ??????????? We did not do the experiment in

which 0cm3 Sodium Thiosulphate and 20cm3 water were used, as there would have

been no reaction. In total, there were always 20cm3 of water and Sodium

Thiosulphate, with 3cm3 Hydrochloric Acid, giving a total solution of 23cm3 ??????????? The black tube was put around and

below the beaker to help prevent any unwanted light from entering the light

probe, as this would have impaired our results. The reason we used a Datalogger and light

probe instead of the old ?cross? method, is threefold. First, human error. The

cross would not just disappear ? it would fade. There would be no specific

point at which the cross would disappear, and the results of your experiment

would be based entirely on a person?s eyesight. Second, this method will only

tell you (albeit inaccurately) when the cross disappeared, i.e. how long it

took for the reaction to get to a certain point of cloudiness. It would not

tell you the varying rates of the reaction. You would not be able to tell if

the reaction speeded up, slowed down, went steady all the way e.t.c. Lastly,

what would you do if the reaction never got as far as making the cross

disappear? Or what if the reaction took a number of hours to get that far? This

traditional method is about as accurate as taking the temperature from a beaker

of water with your finger. To do the experiment, we set up the

apparatus as explained above. We put the various amounts of chemicals into the

beaker, and used the Datalogger and blue box to record the first 3 minutes of

the experiment, and then used the computer to draw up a graph. The blue box was

set to SLOW

and 10k lux.Prediction : I predict that the rate of reaction

will increase (and get more cloudy, more quickly) when the solution of Sodium

Thiosulphate and Hydrochloric Acid are strongest, and there is no water. The

reason for this is that it will be easier for the Sodium Thiosulphate to react

with the Hydrochloric Acid, as they are the only two chemicals in the beaker,

and there is not water to hinder the rate of the reaction. There will also be more Sodium Thiosulphate to react with

the Hydrochloric Acid, regardless of how much water there is.Results : The graphs from the Datalogger are

included in this project. The filename of each graph correspond to the

filenames (DPPAS_xx) listed in the table above. The table below shows the

amount of time that each graph took to level out, i.e. how long the experiment

took to finish. To work out the rate of reaction over the whole reaction (up to

the point where the reaction levelled), I divided the light depreciation (k

lux) by the time taken (minutes) to give a rate of k lux/min. Light

depreciation is k lux at start minus k lux at end of reaction. Here are the

results: Graph Reaction

Finished in k lux at start k lux at end k lux dep./s DPPAS_02 70s 8.9 2.1 .097 DPPAS_03 80s 8.9 2.7 .078 DPPAS_04 100s 8.4 3.2 .052 DPPAS_05 N/A 8.3 N/A N/A ??????????? Analysis

/ Conclusion : Our

results show that, as predicted, the more concentrated solutions reacted more

quickly than the weaker ones. As the concentration got weaker, the reaction was

slower. I would expect the same pattern of you swapped Sodium Thiosulphate and

Hydrochloric Acid for two other chemicals, which are not affected by water, but

will react with each other. There were a few anomalies at the beginning of two of

our

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