66-74. What is the empirical formula of each compound for which the analysis is given below?
66. Analysis: H = 1.24%, Br=98.76%.
67. Analysis: K = 44.9%, S = 18.4%, O = 36.7%.
68. Analysis: Iron = 17.21 g, chlorine = 32.79g.
69. Analysis: K = 28.71%, H=0.73%, S = 23.57%, 0 = 46.99%.
70. Analysis: Ba = 80.2%, 0= 18.7%, H = 1.2%.
71. Analysis: Mg = 27.73%, P = 23.58%, O = 48.69%.
72. Analysis: Cu = 39.79%, S = 20.11%, 0 = 40.10%.
73. Analysis: Mg = 20.18%, S = 26.66%, O = 53.16%.
74. A certain hydrocarbon was found to be 80.0% carbon and 20.0% hydrogen. The molecular weight was determined to be 30. What is the molecular formula?