Part B Follow these steps to complete the table:

Reuse the same test tubes from part A, labeled Fe2+ and Fe3+. Be sure they’re clean.
Add 4 milliliters of iron(II) sulfate to the test tube labeled Fe2+.
Add 4 milliliters of iron(III) nitrate to the test tube labeled Fe3+.
Add 4 milliliters of potassium iodide to each test tube.
Add 1 milliliter of the prepared starch solution to each test tube.
Record your observations, noting any evidence of a chemical reaction. If there is no evidence of a reaction, write “no reaction.”

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol