4. We have 13.9 g sample of impure iron pyrite. The sample is heated to produce iron(III) oxide and sulfur dioxide. If we obtained 8.02 g sample of iron(III) oxide, what was the percentage of iron pyrite in the original sample?

2. a) The oxidation number of an atom is typically the same as the charge of its common ion, therefore O is usually -2. Because magnesium oxide is a neutral compound, what must the oxidation number of Mg be? b) Neutral magnesium nitride that can sometimes be made as a byproduct of this reaction. What is the formula for this ionic compound?

A 7.543 gram sample of manganese is heated in the presence of excess fluorine. A metal fluoride is formed with a mass of 12.76 g. Determine the empirical formula of the metal fluoride.

A 35 mL of a Na3PO4 aqueous solution and 35 mL of a BaCl2 aqueous solution were combined to form 0.520 g of Ba3(PO4)2 precipitate. If reagent tests demonstrated that Na3PO4 was the limiting reactant in the precipitation reaction, calculate the concentration of the Na3PO4 solution.

ABS plastic is a polymer consisting of three monomer units: acrylonitrile (C₃H₃N), butadiene (C₄H₆), and styrene (C₈H₈). A sample of ABS plastic contains 13.7% N by mass. It took 1.56 g of Br₂ to react completely with a 2.00 g sample of ABS plastic. Bromine reacts 1:1 (by moles) with the butadiene units in the polymer and nothing else, so bromination is a method for determining the quantity of butadiene in the polymer. What is the percent by mass of styrene in the polymer?

b. How many grams of copper(i) sulfide could be produced from 28.0 g of copper(l) chloride reacting with an excess of hydrogen sulfide gas?

An impure sample of table salt (NaCl) that was dissolved in water and treated with silver nitrate to form silver chloride. If the initial sample had a mass of 1.741 g and the final mass of the AgCl was found to be 4.084 g, what is the mass percent of NaCl in the impure sample?

Iron ore is impure Fe2O3.  When solid Fe2O3 is heated with an excess of carbon, iron metal, and carbon monoxide are produced.  From a sample of ore weighing 878 kg, 515 kg of pure iron is obtained.  What is the % Fe2O3, by mass, in the ore sample?

A mass of 2.50 g of hydrated copper (II) sulfate is placed in a crucible and heated. On heating, 1.59 g of white anhydrous copper (II) sulfate is left behind. Determine the percentage of water in copper (II) sulfate.

If 2.952 g of copper(II) nitrate is reacted with sufficient sodium hydroxide, how much copper (II) hydroxide will be produced?