MCQ Detailed View

The empirical formula of a compound represents the simplest whole-number ratio of atoms of each element present in the compound. To determine the empirical formula, the following steps are applied:

Step 1: Write down the masses of each element given in the problem.

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  Carbon (C) = 24 g

  
  


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  Hydrogen (H) = 2 g

  
  


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  Oxygen (O) = 64 g

  
  

Step 2: Convert the masses into moles using atomic weights.

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  Atomic weight of C = 12, so moles of C = 24 ÷ 12 = 2

  
  


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  Atomic weight of H = 1, so moles of H = 2 ÷ 1 = 2

  
  


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  Atomic weight of O = 16, so moles of O = 64 ÷ 16 = 4

  
  

Step 3: Express the values as a mole ratio.
C : H : O = 2 : 2 : 4

Step 4: Simplify to the smallest whole numbers.
Dividing each value by 2 → 1 : 1 : 2

Step 5: Write the empirical formula.
The formula becomes CHO₂.

This means the compound has one atom of carbon, one atom of hydrogen, and two atoms of oxygen in its simplest form.

Why CHO₂ and not another option?

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  C₂H₂O₄ → This is a multiple of CHO₂ (molecular formula could be C₂H₂O₄, but not empirical).

  
  


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  CH₂ → Ratio is 1:2, does not fit given data.

  
  


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  CH₂O → Ratio is 1:2:1, also does not fit.

  
  


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  CHO₂ → Correct simplest ratio 1:1:2.

  
  

Key Concept:
The empirical formula provides the basic composition of a compound. In some cases, the molecular formula is a multiple of the empirical formula, but for exam questions, the mole ratio simplification is crucial.

Thus, the empirical formula of the compound is CHO₂.