Inorganic Chemistry and Applications (CHEM 2400) ____________________________________________________________ ____________________________________________________________ Laboratory Manual - 2017 Experiment #2: page 1 of 2 Experiment 2 Preparation of Barium Peroxide Introduction: Simple inorganic peroxides can be classified as hydroperoxides, characterized by the HO2 - ion, peroxides- by the O2 2- ion, superoxides and ozonides, characterized by the O2 - and O3 - ions, respectively. The difference in the nature of the –O-O- bridging bonds as found in peroxides, hydroperoxides, superoxides, and ozonides can be demonstrated by simple chemical means, such as reactions of these compounds with water. The hydrolysis of both peroxides and hydroperoxides proceeds as follows: M a Group 1 metal O2 O MOH H 2 MOOH H 2 O2 O 2MOH H 2 2H 2 O2 M        Peroxides and hydroperoxides, therefore, can be considered as derivatives of hydrogen peroxide, when one or both hydrogen atoms are replaced by a metal. In contrast, the hydrolysis of superoxides produces the unstable intermediate HO2· radical, hydroperoxyl: However, hydrogen peroxide is not a product of hydrolysis of ozonides: 2 O 4MOH 5O 2 2H 3 4MO    (From Peroxides, Superoxides, and Ozonides, I.I. Volnov, Plenum Press, New-York, (1966)). Barium peroxide, the first known peroxide compound, can be obtained by oxidizing BaO with air in a muffle furnace at 500-520 °C in the presence of a small amount of water pressure. Barium peroxide can also be formed by the reaction of barium oxide hydrate with hydrogen peroxide or from solutions of barium chloride, or barium nitrate with hydrogen peroxide. It has a cream colour which is probably caused by the presence of superoxide. Barium peroxide cannot be decomposed by water, nor does it dissolve in water or organic solvents and can be readily separated from soluble compounds, and even barium oxide. It reacts with diluted aqueous acid solutions to form corresponding salts and hydrogen peroxide. 2 O 2 O 2 O 2MOH H 2 2H 2 2MO 2 O 2 O 2 H 2 2HO 2 O 2MOH 2HO 2 2H 2 2MO              Inorganic Chemistry and Applications (CHEM 2400) ____________________________________________________________ ____________________________________________________________ Laboratory Manual - 2017 Experiment #2: page 2 of 2 Barium peroxide forms a series of molecular compounds with water and hydrogen peroxide, of which BaO2∙8H2O is the most stable. In fact, it is the most thermally stable of all the known metal peroxides. It extensively liberates oxygen only at a temperature above 500 °C, if heated at atmospheric pressure. The reaction of barium peroxide with acids depends on the condition.  With anhydrous HCl the following reaction occurs: 2 O Cl2 O2 4H 2 8HCl 3BaCl 2 3BaO       With aqueous solutions of the same acid, barium peroxide forms hydrogen peroxide: 2 O2 H 2 2HCl BaCl 2 BaO    Barium peroxide is used in pyrotechnics, tracer ammunition, in manufacturing of lubricating oil detergents, in the production of synthetic gas CO + H2; cracking high boiling point hydrocarbons, in delayed igniting composites (along with powdered manganese, selenium or tellurium) etc. Preparation of Barium Peroxide Provided solutions: 6 % hydrogen peroxide Part I Prepare 20 mL of 1:1 (by volumes) hydrochloric acid solution. Add slowly 7.5 g of barium carbonate in small portions while stirring the mixture with a glass rod until some of the carbonate remains undissolved. A small additional portion of the barium carbonate may be required. Boil the solution to remove carbon dioxide. Remove unreacted barium carbonate by vacuum filtration of a hot mixture. Keep the filtrate. Prepare (in a fume hood) a solution by mixing 5 mL of concentrated aqueous ammonia and 10 mL H2O. Then add 30 mL of 6% hydrogen peroxide and cool the solution on ice. Add the barium chloride solution (the filtrate) dropwise (use a Pasteur pipette) to the hydrogen peroxide containing solution while stirring continuously. Allow the solution to stand in ice for 20-30 minutes and collect the precipitated product on a pre-weighed porous (M) crucible. Wash with several small (three 2-3 mL) portions of cold water and finally with acetone. Insert the crucible into a beaker and put in an oven. Dry at approximately 60 °C for 10-15 minutes. Report the mass of the Barium Peroxide which you obtained, not the % yield. Record all chemical reactions, carried out in the experiment. Inorganic Chemistry and Applications (CHEM 2400) ____________________________________________________________ ____________________________________________________________ Laboratory Manual - 2017 Experiment #2: page 3 of 2 Part II Prepare 20 mL of approximately 4 M of H2SO4 (do the calculation at home). Dissolve your barium peroxide in 10-15 mL ice-cold 4 M H2SO4 solution. Filter the mixture using gravity filtration. Add iron powder (approximately 0.1 g) to the filtrate in a test tube and warm the mixture in a boiling water bath. Write the reaction between Fe(s) and H2SO4 and between the product of this reaction with H2O2. References: [2], [3], [5], [13], [14] http://en.wikipedia.org/wiki/Hydrogen_peroxide Due date: the day, when you perform your next experiment. Questions: 1. Provide a brief MSDS description for barium peroxide. 2. Why is magnesium hydroxide a much more effective antacid than calcium and barium hydroxide? 3. Identify A, B, C, and D. No reactions are required. C H2O carbon Ba +H2O→A + CO2→ B HCl D

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