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When iodine reacts with starch, the solution will turn a brownish colour.
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∙ 15y ago
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Bread gives black-blue color with the iodine why?
bread gives black-blue or deep blue color with iodine because starch is present in bread. ...
What is the result of lugol's test in glycogen?
it should give dark brown color with high concentration of glyogen
Why does iodine change its colour?
This phenomena depends upon the what is tested. iodine test usually gives a positive result of blue color for starch. The blue color is caused by the trapping of the iodine inside the structure of the starch (note that starch is a polyssacharide that has a helical structure). It is only with starch that this happens cause starch has the only one with a helical structure. Now your question is why is it that the color disappears when heated, right? This is because the heat causes an unwinding of the helical structure of starch releasing the trapped iodine making the solution colorless. However, if cooled, with no heat present, the starch structure becomes helical once more trapping the iodine returning the blue colored solution. this is just what i learned from my Biochemistry class, hope it helps!!
How long did the starch react with achromatic point?
Achromatic means "without color." During a hydrolysis test, starch auger is used to grow bacteria. An iodine reagent is used to flood the plate. The starch is dyed a blue-brown color. Areas where the starch has been completely digested by the bacteria, are clear. That is known as the achromatic point, or the point at which all the starch has been consumed and the iodine does not dye the auger.
How can you tell when hydrolysis of starch is complete?
If using acid-catalyzed hydrolysis of starch you can tell the hydrolysis is complete with the solution no longer gives a bluish/purple color with iodine solution. The color should be colorless.
What chemical test is performed to indicate the completion of the hydrolysis of starch by acid?
If using acid-catalyzed hydrolysis of starch you can tell the hydrolysis is complete with the solution no longer gives a bluish/purple color with iodine solution. The color should be colorless.
Why does Iodine test gives blue color with starch but red with glycogen?
Iodine forms colour complexes with polysaccharides. The colour of the complex depends of the 3d structure of the polysaccharide. Starch is a coiled structure, which turns blue when bound to IKI (iodine solution), whereas glycogen, which is a branched molecule, turns red/brown.
Why iodine is used in starch hydrolysis test?
Iodine in water solutions is usually colored strong enough so that its presence can be detected visually. However, close to the end point, when the iodine concentration is very low, its yellowish color is very pale and can be easily overlooked. Thus for the end point detection starch solutions are used.
Why you add mercuric iodide in starch indicator preparation?
It gives an obvious color change. It's preparation is simple and easy plus it's not harmful or hazardous. When starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. The complex is very useful for indicating redox titrations that involve iodine because the color change is very sharp. It can also be used as a general redox indicator: when there is excess oxidizing agent, the complex is blue; when there is excess reducing agent the color disappears.
What is the function of starch solution in the redox titration?
It is used as indicator for the endpoint of a Iodometric (redox) titration: it gives a bluish grey to black color with very minute excess of Iodine-iodide ions (I3-)
Why you use iodine to test the presence of starch but why not other chemicals?
Because it call sense the difference between a base and an acid.
What is achromic point?
The point in time during the action of amylase on starch at which the reaction mixture no longer gives a colour with iodine, i.e. the reaction has proceeded to the point when the starch has all been degraded at least as far as achröodextrins.
