Question

the student conducted three experiments in order to test if water and oxygen in the environment rust steel nails. they used appropriate safety equipment and followed all safety procedures. three separate steel nails were placed in separate test tubes, each containing different substances. all three test tubes were sealed with stoppers.
in test tube 1, the nail was partially placed in water.
in test tube 2, the nail was submerged in water that was boiled to remove oxygen and a layer of oil was added to prevent oxygen from re - entering the water.
in test tube 3, the nail was enclosed in air and a chemical (anhydrous calcium chloride) that removes water vapor from the air.
the nails were left in the test tubes for approximately three weeks. an experimental setup model representation of the experiment is shown below. the results of the experiment are shown in the table below.
3 based on the experimental results the student claims that the reactant, wate,r does not result in the product of rust. use information from the chemical reaction to refute this claim.

Explanation:

Step1: Recall rust - formation reaction

Rust formation is a redox reaction where iron (in steel nails) reacts with oxygen and water to form iron(III) oxide (rust). The general chemical equation is \(4Fe + 3O_{2}+6H_{2}O
ightarrow 4Fe(OH)_{3}\), which can decompose to \(2Fe_{2}O_{3}\cdot3H_{2}O\) (rust).

Step2: Analyze test - tube 1

In test - tube 1, the nail is partially in water and in contact with air (oxygen). Rust is formed. This shows that both water and oxygen are involved in the rust - formation process. Water provides the medium for the electrochemical reaction to occur and is a reactant in the overall rust - formation reaction.

Step3: Analyze test - tube 2

In test - tube 2, the nail is in water with no oxygen (boiled water and oil layer). No rust is formed. This indicates that without oxygen, even in the presence of water, rust does not form. But it does not mean water is not a reactant.

Step4: Analyze test - tube 3

In test - tube 3, the nail is in air with no water (anhydrous calcium chloride removes water vapor). No rust is formed. This shows that water is necessary for rust formation along with oxygen.

Answer:

The claim that water does not result in the product of rust is incorrect. The rust - formation reaction \(4Fe + 3O_{2}+6H_{2}O
ightarrow 4Fe(OH)_{3}\) shows that water is a reactant. In test - tube 1, where both water and oxygen are present, rust is formed. In test - tube 3, without water, no rust is formed, indicating water's essential role in the rust - formation process.