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Which of the following is a correct observation for a chemical change?

  • a)
    The process is always reversible.

  • b)
    A new substance is formed.

  • c)
    No energy change occurs.

  • d)
    The composition remains unchanged.

Correct answer is option 'B'. Can you explain this answer?
Most Upvoted Answer
Which of the following is a correct observation for a chemical change?...
Formula of Rust

Rust is a common name for a very common compound, iron(III) oxide. The chemical formula for rust is Fe2O3. It is also known as ferric oxide.

Explanation:

1. Rust Formation:
- Rust is formed when iron or its alloys, such as steel, are exposed to oxygen and moisture for a prolonged period of time.
- The process of rust formation is a type of corrosion called oxidation, which occurs when iron reacts with oxygen in the presence of water.

2. Chemical Formula:
- The chemical formula for rust is Fe2O3, which indicates that each rust molecule consists of two iron atoms bonded with three oxygen atoms.
- The ratio of iron to oxygen in rust is 2:3, hence the formula Fe2O3.

3. Balanced Chemical Equation:
- The formation of rust can be represented by the balanced chemical equation:
4Fe + 3O2 + 6H2O → 4Fe(OH)3
- In this equation, iron reacts with oxygen and water to form hydrated iron(III) oxide, which is commonly known as rust.

4. Appearance and Properties of Rust:
- Rust appears as a reddish-brown or orange powder, which is a result of the iron(III) oxide compound.
- It is a brittle material that easily flakes off from the surface of the iron or steel it forms on.
- Rust is also known for its porous nature, allowing it to absorb and retain moisture, which further accelerates the corrosion process.

Conclusion:

In conclusion, the chemical formula for rust is Fe2O3. It is formed when iron reacts with oxygen and water, resulting in the formation of iron(III) oxide. Rust is a common occurrence in iron and steel objects exposed to the environment, and it is undesirable as it weakens the structural integrity of the material.
Community Answer
Which of the following is a correct observation for a chemical change?...
Option B has Iron ( Fe2), oxygen ( O3) and water ( H2O), which is how rust forms on iron ( with moisture, oxygen and water).
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Which of the following is a correct observation for a chemical change?a)The process is always reversible.b)A new substance is formed.c)No energy change occurs.d)The composition remains unchanged.Correct answer is option 'B'. Can you explain this answer?
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