NECO 2009 Chemistry · Question 23

C6_6H12_{12}O6_6 What is the molar mass of the compound above? [ H=1, C=12, O=16 }

Options

  1. A.45
  2. B.61
  3. C.180
  4. D.123
  5. E.244

Answer: C. 180

Explanation written with AI and checked against the answer key

Analyze the question: You are asked for the molar mass of glucose, C₆H₁₂O₆, using the atomic masses H = 1, C = 12, O = 16.

Concept: Molar mass is the sum of the atomic masses of all atoms in one formula unit of the compound. Multiply each element's atomic mass by the number of atoms of that element, then add the results.

Solution:

  • Carbon: 6 × 12 = 72
  • Hydrogen: 12 × 1 = 12
  • Oxygen: 6 × 16 = 96

Molar mass = 72 + 12 + 96 = 180 g/mol

Tip: For C₆H₁₂O₆, notice that the formula is (CH₂O)₆. The mass of one CH₂O unit is 12 + 2 + 16 = 30, and 30 × 6 = 180. Learning this shortcut helps you check carbohydrate molar masses quickly. Also remember that the other options are distractors, so always add up each element's contribution carefully.

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