In Organic Chemistry, Benzene is the absolute king of all aromatic compounds. It is a highly flammable, sweet-smelling liquid with a massive, perfect hexagonal ring structure.
To solve any stoichiometry problem involving this chemical, you must know its weight. The exact, universally accepted Molar Mass (Molecular Weight) of Benzene is 78.11 g/mol.
Chemical Name: Benzene.
Chemical Formula: C₆H₆.
Exact Molar Mass: 78.11 g/mol.
School Exam Mass: 78 g/mol.
Unit of Mass: Always written in 'grams per mole' (g/mol) or Unified Atomic Mass Units (u).
Before you can calculate the mass of any chemical, you must know its exact biological recipe. The chemical formula of Benzene is C₆H₆. This means one single massive ring of Benzene is perfectly built using exactly 6 Carbon (C) atoms heavily bonded to 6 Hydrogen (H) atoms.
To calculate the massive total weight, we simply look at the Periodic Table and add the weights of all the individual atoms together.
Atomic Mass of Carbon (C) = 12.011 g/mol. Since there are exactly 6 Carbon atoms: 6 × 12.011 = 72.066 g/mol.
Atomic Mass of Hydrogen (H) = 1.008 g/mol. Since there are exactly 6 Hydrogen atoms: 6 × 1.008 = 6.048 g/mol.
Calculate the Final Total Mass: Total Mass = Mass of Carbons + Mass of Hydrogens Total Mass = 72.066 + 6.048 = 78.114 g/mol.
In school-level chemistry (Class 11 and 12 exams), examiners do not want you wasting massive amounts of time calculating decimal points. Therefore, textbooks universally round the atomic masses (Carbon = 12, Hydrogen = 1). Using this fast method: (6×12) + (6×1) = 72 + 6 = Exactly 78 g/mol.
The highly accurate molecular mass of Benzene (C₆H₆) is 78.11 g/mol.
You must use the exact formula C₆H₆ (6 Carbons and 6 Hydrogens) to mathematically calculate its weight.
For faster human calculation during tough exams, the complex decimal atomic weights are rounded off (C=12, H=1). Multiplying (12×6) + (1×6) yields exactly 78.
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