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Chemistry Titration. watch

1. Hey,

Im doing a titration for my Chemistry Investigation. Its "Which brand of bleach is most cost effective?"

Im neutralizing three brands of bleach, high, medium and low quality with sulfuric acid. If I'm correct, the more acid needed to neutralize it, the better quality the bleach. If there is a huge difference in the amount of bleach needed to neutralize it, then it may not be cost effective. But if there is not much difference, the high quality would be more cost effective. The difference in price would also determine this.

I guess I am measuring the cost of the bleach compared to the amount of bleach needed to neutralize it.

Its all very confusing, I was hoping if anyone could shed some more light, if they can understand the experiment.

Thank you.
2. By the sounds of it, you're going to want to work out the moles of alkali per bottle of bleach. To do this, you'd take a fixed quantity of bleach from each one, titrate it against a known quantity and concentration of acid, and use simple calculations to find out the concentration of alkali. Then, multiply the concentrations by the volume of the bottles, to find out the total number of moles of bleach per bottle.

From here, you could take the cost of the bottle, and divide this by the number of moles of alkali in the bottle, to find out price per mol of alkali for each brand of bleach, the higher the value, the lower the cost effectiveness of the bleach. However, you might want to consider whether this determines the quality of the bleach, as bleaches have other cleaning agents that are important as well.
3. Ah thanks very much. How would I work out the concentration of the acid? At school Im pretty sure we get dilute acid and no concentration indicated. Its volume/mass right?

For example, I would titrate 25ml of each bleach against Xml of acid (However much the burette allows). I would use universal indicator or a pH meter to get it to a neutral state. Calculate the concentration with the formulae, then multiply the conc. by the volume as you said.
4. You should have standard molarity acid available.

If not, you could make it up using solid acid as you would make a standard solution (unlikely here, pure H2SO4 is liquid at room temperature and it'd be pretty dangerous to work with), or find your concentration by titrating your acid against a known concentration of base.
5. Righty-ho. Im a lot more confident now. Thanks guys.

Ah yeah, for my preliminary experiment, I plan to use the 2/3 acids available to me and titrate it against one type of bleach to find out which acids gives the best results. I believe I want more spread out results to determine which acid to use, also making it easier to plot.
6. Ok firstly, are you doing GCSE Chemistry?

Secondly, if you have unknown concentration of acid, you can still work out a comparitive ratios between the bottles of bleach, substitute all of your concentrations for the acid with X. It'll work out as a comparitive ratio, but no data on price per mole. You should probably ask the concentration of the acid at your school. =P

If they refuse, work it out (assuming it is a strong acid (H2SO4, HCL)) and make the assumption that it dissociates completely. Measure the pH of the acid, use pH=-log[H+] to work out the concentration of H+ ions, which, because of the full dissociation, will also give you the concentration of the acid in relation to the water. I.e. if [H+] comes out as 1(moldm^-3) you can assume that the HCl or H2SO4 solution initially was 1moldm^-3... I think.
7. Yep I am. Ill just ask my teacher. The easiest/laziest option :P

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