How Is Carbon Calculated in Cementite and What Is Its Role in Pearlite?

[p.mather]

Fe3C Cementite HELP PLEASE!

Hello... I was wondering if someone would be able to help with the follow question...

Cementite: consider cementite. Calculate the amount of carbon in Cementite (1) as atomic % (2) as weight % [atomic weights Fe 56, c 12]. Place cementite on the Fe-C phase diagram; explain the nature of its appearance on the diagram, and comment on the nature and properties of cementite. Cementite is a key part of pearlite- how does it contribute to the structure of pearlite?

I totally understand the question apart from the atomic % and the weight %, if someone could help i would be so grateful, thanks.

 

[chemisttree]

The formula is Fe₃C. That is three iron atoms per carbon. Express that ratio in terms of atoms Fe:total atoms in the formula to get Fe atomic %. Also find C:total atoms in the formula to get C atomic %. Convert that to weight to get Weight %.

 

[p.mather]

The formula is Fe₃C. That is three iron atoms per carbon. Express that ratio in terms of atoms Fe:total atoms in the formula to get Fe atomic %. Also find C:total atoms in the formula to get C atomic %. Convert that to weight to get Weight %.

could you give me a example as this really isn't my strong point, thanks

 

[Redbelly98]

Fe₃C contains ___ iron atoms, ___ carbon atoms, and ___ atoms in total.
Using those numbers, what percentage of the total atoms are carbon?

 

[DeeNos]

Sure, I can help you with your question about cementite. First, let's start with defining cementite. Cementite, also known as iron carbide, is a compound of iron and carbon with the chemical formula Fe3C. It is a hard and brittle material with a high melting point and is commonly found in steel alloys.

Now, to calculate the amount of carbon in cementite, we can use the atomic and weight percentages. Since the molecular weight of Fe3C is 183.16 g/mol (56 g/mol for Fe and 12 g/mol for C), we can calculate the percentages as follows:

(1) Atomic % of carbon in Fe3C = (12 g/mol / 183.16 g/mol) x 100% = 6.55%

(2) Weight % of carbon in Fe3C = (12 g/mol / 183.16 g/mol) x 100% = 6.55%

Next, let's place cementite on the Fe-C phase diagram. The Fe-C phase diagram is a graphical representation of the phases of iron and carbon at different temperatures and carbon concentrations. Cementite is located in the upper right corner of the diagram, indicating that it is a high-temperature, high-carbon phase.

The appearance of cementite on the phase diagram shows that it is a metastable phase, meaning that it is not the most thermodynamically stable phase at that temperature and carbon concentration. It is surrounded by other phases such as ferrite, austenite, and graphite, which are more stable.

As for the properties of cementite, it is a hard and brittle material with a high melting point. It is also a very strong phase, which contributes to the strength and hardness of steel alloys. However, it is also prone to cracking, which can cause failure in the material.

In pearlite, cementite is present in the form of lamellae (layers) embedded in a matrix of ferrite. This lamellar structure gives pearlite its unique appearance and contributes to its strength and toughness. Cementite acts as a strengthening phase, while ferrite provides ductility.

I hope this helps to answer your question about cementite. Let me know if you have any further questions.