Question

1. it’s not unusual for students who see this demonstration to claim that the “red stuff” is rust (meaning the compound iron iii oxide). brainstorm some empirical data (information that you could collect in the lab) that would prove or disprove the claim that the “red stuff” is rust. this is a hard question! really stop and think.

Explanation:

Step1: Analyze rust composition

Rust is iron(III) oxide ($Fe_2O_3$). We can check for iron and oxygen.

Step2: Test for iron

Perform a flame - test or use a chemical reaction like adding a strong acid (e.g., hydrochloric acid). If it's iron(III) oxide, iron ions will be released. For example, with hydrochloric acid: $Fe_2O_3 + 6HCl=2FeCl_3 + 3H_2O$. Then, we can use a reagent like potassium thiocyanate ($KSCN$) to test for iron(III) ions. Iron(III) ions react with $KSCN$ to form a blood - red complex: $Fe^{3+}+3SCN^-
ightleftharpoons Fe(SCN)_3$.

Step3: Test for oxygen

We can try to decompose the "red stuff" if possible. If it contains oxygen, upon decomposition, we might be able to detect oxygen gas. For example, if we heat iron(III) oxide in the presence of a reducing agent like carbon monoxide ($CO$), the reaction is $Fe_2O_3 + 3CO = 2Fe+3CO_2$. We can then test for the presence of carbon dioxide (by passing the gas through lime - water, which turns milky if $CO_2$ is present).

Answer:

Perform acid - reaction and iron - ion test, and test for oxygen through decomposition and product - detection.