試題詳解

86. Carminic acid, a naturally occurring red pigment extracted from the cochineal insect, contains 53.66% C, 4.09% H and 42.25% O by mass. A titration required 10.00 mL of 0.5 M NaOH to neutralize 2.46 g carminic acid. Assuming there is only one acidic hydrogen per molecule, what is the empirical formula and molecular formula of carminic acid? (Na = 23.0 g/mole)
(A) empirical formula: C₂₂H₂₀O₁₃； molecular formula: C₄₄H₄₀O₂₆
(B) empirical formula: C₂₂H₂₀O₁₃； molecular formula: C₂₂H₂₀O₁₃
(C) empirical formula: C₄₄H₄₀O₂₆； molecular formula: C₂₂H₂₀O₁₃
(D) empirical formula: C₂₆H₂₀O₁₀； molecular formula: C₂₆H₂₀O₁₀
(E) empirical formula: C₂₆H₂₀O₁₀； molecular formula: C₅₂H₄₀O₂₀