A compound is found to contain 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empi

JAMB Chemistry 2023 61 views

A compound is found to contain 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of the compound?

  1. CH₂O ✓
  2. C₂H₄O₂
  3. C₆H₁₂O₆
  4. C₄H₈O₄

Explanation

Step 1: Convert percentages to grams (assume 100g sample)
Carbon (C) = 40 g
Hydrogen (H) = 6.7 g
Oxygen (O) = 53.3 g

Step 2: Convert grams to moles using atomic masses
Moles of C = 40 ÷ 12 = 3.33 moles
Moles of H = 6.7 ÷ 1 = 6.7 moles
Moles of O = 53.3 ÷ 16 = 3.33 moles

Step 3: Divide by the smallest number of moles
Smallest = 3.33
C: 3.33 ÷ 3.33 = 1
H: 6.7 ÷ 3.33 = 2
O: 3.33 ÷ 3.33 = 1

Step 4: Write the empirical formula
The ratio is C:H:O = 1:2:1
Empirical formula = CH₂O

Remember: The empirical formula shows the simplest whole-number ratio of atoms. C₂H₄O₂ and C₆H₁₂O₆ are molecular formulas that are multiples of CH₂O.

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