Write and balance the molecular equation when aqueous solutions of K2S and Os(SO4)2 are mixed.

Excess Na2SO4(aq) is added to a 4.41×102 mL sample of industrial waste containing Ba2+ ions. If 55.5 g of BaSO4(s) are precipitated from the reaction, what was the molar concentration of Ba2+ in the original sample?

Fe(lI) can be precipitated from a slightly basic aqueous solution by bubbling oxygen through the solution, which converts Fe(ll) to insoluble Fe(lI): 4Fe(OH)*(aq) +40H¯(aq)+O2(g) +2H,0(1) → 4Fe(OH),(s) How many grams of O2 are consumed to precipitate all of the iron in 50.0 mL of 0.0950 MFe(II)?

You are asked to determine the percentage of the components of a mixture containing sodium iodide, NaI, magnesium hydroxide, Mg(OH)2, and barium sulfate, BaSO4. The total mass of your mixture sample is 4.82g. First  you  extracted the NaI from the mixture with water and filtered insoluble Mg(OH)2 and BaSO4 from the solution, containing the NaI. After evaporating and drying the filtrate, you find that you have recovered 0.95g of NaI. When you react the insoluble residue of Mg(OH)2 and BaSO4 with 3M HCl, the Mg(OH)2 dissolves. After  decanting the supernatant liquid containing aqueous MgCl2 from the insoluble BaSO4 and drying the solid, you recover 2.04g of BaSO4. Finally you add 3M KOH solution to the aqueous solution to precipitate the Mg(OH)2. After filtering thesolution and drying the precipitate, you recovered 1.21g of Mg(OH)2.   Calculate the percent Mg(OH)2 in the original sample mixture.