Which factors affect reaction rate?3rd April 2009

content from various sources, compiled by H Graham BSc PGCE

http://www.made-in-china.com/image/2f0j00KvqEgYelHGpdM/Sodium-Thiosulphate.jpg

sodium thiosulphateNa2S2O3

http://www.easy2source.com/products/images/524.jpg

hydrochloric acid HCl

Na2S2O3

HCl

SSO2

NaClH2O

Use these to build the chemical equation

http://www.123helpme.com/view.asp?id=48253Safety

There are a lot of safety issues we must abide by in this experimentalso. We must remember that the substances which we use in thisexperiment can be very harmful if used the wrong way.

When we do this experiment, it may be necessary to wear safetygoggles, as things are very unpredictable, and even though it is veryunlikely that the solution would come out of the beaker during theexperiment, one must still be cautious of spills.

We must make sure that coats and bags are all out of the way whiledoing the experiment. Ties and hair should be tucked out of the way,so they do not make contact with any of the chemicals. It would alsobe preferable to wear a scientific apron, however this is notessential.

We should also try our best not to spill any chemicals, and we mustnot eat or drink in the lab while dealing with these harmfulchemicals, as they can get on to our hands.

Procedure

Firstly, we drew a black cross on a white piece of paper. Then, we put5 cm3 of hydrochloric acid in a beaker, and then put the beaker on theblack cross on the paper. We then added 50 cm3 of Sodium Thiosulphateto the hydrochloric acid, and at this time we do not need to add anywater. . Immediately, we started the stopwatch. We then waited for theblack cross to be completely hidden by the mixture. When thishappened we stopped the stopwatch. By this time the mixture wascompletely cloudy. Then we recorded what the time was.

We then emptied out the contents of the beaker, cleaned it out anddried it out. Next, we added 45 cm3 of Sodium Thiosulphate; we keptthe HCl acid constantly at 5 cm3. Now, because we have to keep thevolume the same for it to be a fair test, we added 5 cm3 of water. (Wehad to add the Sodium Thiosulphate and the water at the same time forthis to be a fair test also). We then recorded the time for the crossto become completely obscured.

We repeated this many times, adding different amounts of SodiumThiosulphate and water each time, and recording the time taken eachtime.

X

volume thiosulphatetime (seconds)

volume acidtemperature

concentration

RESULTS?

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plot results as line graph?

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http://www.yenka.com//file/download.action?id=2294&filename=LR15041504a.swf

How could this investigation be developed?

Design your own procedure