Calculate the quantities with complete solution. (a) mass in grams of 1.95 x 10^26 HCI (b) number of atoms in 35g Fe (c) number of molecules in 1.55 mol O2  (d) mass in kg of 0.49 mol CO2 (e) number of moles of 0.95kg H2O   plssss help me answer these questions, thank you!!!!

Lead poisoning has been a hazard for centuries. Some scholars believe that the decline of the Roman Empire can be traced, in part, to high levels of lead in water from containers and pipes, and from wine that was stored in leadglazed containers. If we presume that the typical Roman water supply was saturated with lead carbonate, PbCO3 (Ksp = 7.4 1014), how much lead will a Roman ingest in a year if he or she drinks 1 L/day from the container?

Gold metal will dissolve only in aqua regia, a mixture of concentrated hydrochloric acid and concentrated nitric acid in a 3:1 volume ratio. The products of the reaction between gold and the concentrated acids are AuCl4-(aq), NO(g), and H2O. The equation for this reaction where HNO3 and HCl are strong acids is Au(s)+4Cl(aq)+4H+(aq)+NO3(aq)AuCl4(aq)+NO(g)+2H2O(a) What stoichiometric ratio of hydrochloric acid to nitric acid should be used? (b) What volumes of 12 M HCl and 16 M are HNO3 required to furnish the Cl- and NO3- ions to react with 25.0 g of gold?

When 10. L of water is added to 3.0 L of 6.0 M H2SO4, what is the molarity of the resulting solution? Assume the volumes are additive.