Carbohydrates have the general formula C_x(H₂O)_y. In which of the following pairs is x not equal to y?

Correct answer: maltose and starch.

Explanation: The “carbohydrate” pattern C_x(H₂O)_y has x = y for simple sugars (monosaccharides), but not for disaccharides/polysaccharides formed by condensation (they lose water).

• Glucose C₆H₁₂O₆ ⇒ x = 6, y = 6 (x = y)
• Fructose C₆H₁₂O₆ ⇒ x = 6, y = 6 (x = y)
• Sucrose / Maltose C₁₂H₂₂O₁₁ ⇒ x = 12, y = 11 (x ≠ y)
• Starch (C₆H₁₀O₅)_n ⇒ effectively x = 6n, y = 5n (x ≠ y)

Therefore, the pair in which both members have x ≠ y is maltose and starch.