Calculate the percentage by mass of the indicated element in the following compounds:
(a) Carbon in acetylene, C2H2, a gas used in welding
(b) Hydrogen in ascorbic acid, HC6H7O6, also known as vitamin C
(c) Hydrogen in ammonium sulfate, (NH4)2SO4, a substance used as a nitrogen fertilizer
(d) Platinum in PtCl2(NH3)2, a chemotherapy agent called cisplatin
(e) Oxygen in the female sex hormone estradiol, C18H24O2
(f) Carbon in capsaicin, C18H27NO3, the compound that gives the hot taste to chili peppers.