chemistry hw.. experiment
2007-02-23 18:15:53 · 2 answers · asked by dian 2 in Science & Mathematics ➔ Chemistry
Iodine is not very soluble in aqueous solutions, so it is usually treated with Potassium iodide to form the Iodine solution that you used. The reactive ingredient is not just the Iodine dimer molecule, but a species called triiodide [I3-]. It looks like three Iodine atoms in a row and has a negative charge.
Starch is a polymer made of glucose units. It has two different forms. One of these is called amylose. It has a specific bonding which allows it to form a coil spring structure.
When the triiodide anion slides inside this spiral coil forming the starch-iodine complex, the solution will become a dark blue-black color. This is called a positive test for starch. It is really a positive test for amylose and not for amylopectin (another form of starch).
2007-02-23 19:39:32 · answer #1 · answered by Richard 7 · 11⤊ 0⤋
the iodine will bind with the open O in starch and turn the solution a dark indigo.
2007-02-24 02:18:36 · answer #2 · answered by summi_bear 2 · 0⤊ 0⤋