Question

1. explain when powdered iron is left exposed to the air, it rusts. explain why the mass of the rust is greater than the mass of the powdered iron. 87. explain discuss the statement “a gas requires a container, but a solid is its own container.”

Explanation:

Question 86

Step1: Identify the reaction

Rusting is a chemical reaction where iron (\(Fe\)) reacts with oxygen (\(O_2\)) and water (\(H_2O\)) from the air. The general reaction is \(4Fe + 3O_2+ 6H_2O
ightarrow 4Fe(OH)_3\) (and further oxidation to \(Fe_2O_3\cdot nH_2O\), rust).

Step2: Apply the law of conservation of mass

The law of conservation of mass states that in a chemical reaction, the total mass of reactants equals the total mass of products. Here, the reactants are iron, oxygen, and water. The product is rust.

Step3: Analyze the mass contribution

The mass of rust is the mass of iron plus the mass of oxygen and water that reacted with it. Since oxygen and water are added to the iron during rusting, the mass of rust (product) is greater than the mass of the original iron (one of the reactants).

• For gases: Gases have particles with high kinetic energy and weak intermolecular forces. They expand to fill any available space. Without a container, gas particles would disperse freely into the surroundings. So a container is needed to confine the gas and give it a defined volume.
• For solids: Solids have particles with strong intermolecular forces, arranged in a fixed, ordered structure. The particles vibrate in place but don't move freely to expand. Thus, a solid maintains its own shape and volume, acting as its own "container" (it doesn't need an external container to hold its shape/volume like a gas does).

Answer:

Rusting is a reaction where iron (\(Fe\)) reacts with oxygen (\(O_2\)) and water (\(H_2O\)) from air (\(4Fe + 3O_2+ 6H_2O
ightarrow 4Fe(OH)_3\), then to rust). By the law of conservation of mass, rust's mass equals iron's mass plus the mass of \(O_2\) and \(H_2O\) that reacted. So rust's mass > iron's mass.

Question 87