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Investigating Bleach.

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Introduction

Investigating Bleach Research My aim is to test my own home made bleach against other name brand bleaches, I will test them for available chlorine. Bleach is any substance that lightens, brightens or removes colour from a material. Manufacturers bleach textiles, paper and many other materials to whiten them or prepare them to be dyed. Homemakers use some bleach to brighten colours. People also use some bleach as disinfectants. There are two main kinds of bleaches:- Chemical and Optical. Chemical bleaches act on coloured molecules that give material colour. The most widely used chemical bleach includes chlorine bleaches and oxygen bleaches. Many household and industrial bleaches are chlorine bleaches, which remove colour from most textiles, wood pulp, pottery and other materials. Oxygen bleaches are milder than chlorine ones. People use hydrogen peroxide and other oxygen bleaches to lighten hair and brighten fabrics and other materials that might be harmed by chlorine bleaches. Chlorine occurs in combined form of sodium chloride. Sodium chloride is found in large quantities in sea water and as rock salt, which was deposited by the evaporation of ancient seas. It is excreted by the electrolysis of sodium chloride either in water or in molten states. Chloride is being formed at the anode. The electrolysis of sodium chloride produces sodium hypochloride, NaOC1, a compound of sodium and oxygen, and chlorine, an element used to kill bacteria, particularly in drinking water and swimming pools. ...read more.

Middle

For this I will need oxidising agent of those available I will use potassium permanganate. apparatus * 250cm3 Conical flask * Thistle funnel * 3 Boiling tube * Delivery system (4 bungs with glass tubes) * Bunsen burner * Bench mat * Sodium hydroxide * Potassium permanganate * Conc. Hydrochloric acid * safety goggles Method The apparatus was set up as shown above ensuring all connections were secure preventing any Cl2 gas from leaking into the room. This was set up in the fume cupboard so the gas escaping the experiment would be extracted from the room. The boiling tubes were each filled approximately half full with the required liquid. In the conical flack I put 20ml of water mixed with 10g potassium permanganate and made sure that the delivery tube from the thistle funnel goes below the water level to stop the chlorine gas travelling back up the tube. Next I added 50ml of conc. HCl however the reaction did not start immediately so I used a Bunsen burner to gentle heat the mixture when ever needed to speed up the reaction. In the conical flask the potassium permanganate is reacting with the hydrochloric acid in this reaction: 2KMnO4 + 16HCl 2KCl + 2MnCl2 + 5Cl2 this gas given off then travels through the H2O and into the sodium hydroxide where it forms bleach the second test tube with NaOH is to neutralise any excess Chlorine gas before being released out of the system. ...read more.

Conclusion

The results from experiment two are the results I will be using when comparing them with the results of the bacterial experiment. I think the first table of results is more likely to be inaccurate because unlike the second experiment, you cannot tell when the reaction has finished. You know when the reaction has taken place in the second experiment because the solution has changed colour. If I had let the reaction go on for a longer time there could have been a higher amount of oxygen given off, but I am not sure how long this reaction takes to work and can only assume it happens within the first few moments. There could also have been a leak in the experiment but because it is a gas I would not be able to see it, where as if I had dropped some of the sodium thiosulphate I would have known. Also there was some gas escaping out of the burette when I tried to drop somehydrogen peroxide into the bleach, there was also a build up of pressure because the glass syringe kept sticking and the gas would bubble up through the hydrogen peroxide. After two trial attempts I discovered this problem, so I placed a rubber bung at the top of the burette but the empty burette would have been filled with oxygen as well. On the next page is a bar chart displaying the two different results. ...read more.

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