# Which of the following structures contains 6.67% of carbon?

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Which of the following structures contains 6.67% of carbon?
1. Ferrite
2. Austenite
3. Pearlite
4.  Cementite

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Correct Answer - Option 4 :  Cementite

Explanation:

• Cementite or Iron Carbide has the chemical formula Fe3C and contains 6.67% carbon by weight.
• It is the hardest structure that appears in the iron-carbon equilibrium diagram.
• Cementite has an orthorhombic crystal structure and is extremely hard and brittle as compared to austenite and ferrite.

Weight % of carbon in cementite $=\frac{12\times100}{3\times56~+~12}=6.67 %$