Sins

"(a). An oxide of manganese was found by gravimetric analy'sisto contain 4.995 g manganese combined with 2.909 g oxygen. Determine its empirical formula." For this question is the answer Manganese20 Oxygen1? Thank you

Double posted on accident, sorry.

Hi, could anyone help me with these... ... (a). An oxide of manganese was found by gravimetric analy'sisto contain 4.995 g manganese combined with 2.909 g oxygen. Determine its empirical formula. (b) When this oxide was strongly heated, a second oxide was formed. 8.777g of this new compound contained 6.110g of manganese. Determine the empirical formula of this second oxide. © Using these empirical formulae, write an equation for the reaction involved in converting the first oxide into the second. 4. One ore of iron is iron pyrites, FeS2 (fool’s gold). What percentage of iron, by mass, does it contain? I'm tried looking for help on googe, but haven't found any. I've tried working them out, but I can't seem to do it. I've worked out every other question on my sheet, I just can't seem to do these. Could anyone work them out, and show how to achieve the workings? Maybe, that'll help me understand how it's done. Thanks