3) in the hydrolysis of disaccharides and polysaccharides portion of the lab, starch should give one positive iodine test and one negative iodine test. explain why.

potassium iodide is the basic test for starch,and the positive test is blue-black coloration, any other test substance which is not starch will give a negative results.

Explanation:

Starch is an example of  polysaccharide  and since the standard test for it is potassium iodide solution, it gives a positive test.

Diasaccharides e.g maltose are reducing sugars.their standard test is BENEDICT test .

Therefore, in the hydrolysis;  starch should give a positve test, while Diasaccharides should give negative rest.