Формула арена, в составе которого (по массе) 90%углерода а) С6 Н6

Дано:
(C в C_xH_y) = 90%

Найти:
C_xH_y - ?

Решение:
1) Mr (C₆H₆) = Ar (C) * N (C) + Ar (H) * N (H) = 12 * 6 + 1 * 6 = 78;
2) (C в C₆H₆) = N (C в C₆H₆) * Ar (C) * 100% / Mr (C₆H₆) = 6 * 12 * 100% / 78 = 92,31%;
3) Mr (C₈H₈) = Ar (C) * N (C) + Ar (H) * N (H) = 12 * 8 + 1 * 8 = 104;
4) (C в C₈H₈) = N (C в C₈H₈) * Ar (C) * 100% / Mr (C₈H₈) = 8 * 12 * 100% / 104 = 92,31%;
5) Mr (C₈H₁₀) = Ar (C) * N (C) + Ar (H) * N (H) = 12 * 8 + 1 * 10 = 106;
6) (C в C₈H₁₀) = N (C в C₈H₁₀) * Ar (C) * 100% / Mr (C₈H₁₀) = 8 * 12 * 100% / 106 = 90,57%;
7) Mr (C₉H₁₂) = Ar (C) * N (C) + Ar (H) * N (H) = 12 * 9 + 1 * 12 = 120;
8) (C в C₉H₁₂) = N (C в C₉H₁₂) * Ar (C) * 100% / Mr (C₉H₁₂) = 9 * 12 * 100% / 120 = 90%.

Ответ: Вариант д) C₉H₁₂.