Question

What type of change, physical or chemical, occured upon mixed the two solutions? Explain your reasoning...

What type of change, physical or chemical, occured upon mixed the two solutions? Explain your reasoning from the reaction, potassium iodate and starch indicator(H2SO4 and NaHSO3)

Homework Answers

Answer #1

In analytical methods involving iodine, normal redox indicators are not necessary, because starch is available, a sensitive internal indicator that experiences a highly specific interaction with iodine. The free iodine forms a very intense blue color with dispersed colloidal starch and this coloration serves as an indication of the presence of iodine.

An amount as small as 2 x 10-7 M iodine gives a noticeable blue color with starch.

In the presence of iodide in 10-5 M concentration the blue color of starch-iodine can be easily seen with a concentration of 5 x 10-6 M iodine.

As can be seen, the starch-iodine method is no more sensitive than the self-coloring of iodine, but the blue color of the starch-iodine is more distinctive, in particular in colored solutions.

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