W = Ar (элемента) * n / Mr (вещества) * 100% w(C) = (12* 12 / 342) * 100% = 42,1% w(H) = (1 * 22 / 342) * 100% = 6,43% w(O) = (16 * 11 / 342) * 100% = 51,46%