Magnesium reaction with sulfuric acid

DOT CLASSIFICATION 6.1 Label Poison SAFETY PROFILE A poison. Moderately toxic by ingestion. Mildly toxic by skin contact. Mutation data reported. Mixtures with magnesium are hypergolic on contact with nitric acid. Forms extremely explosive addition compounds with hexanitroethane. Vigorous reaction with sulfuric acid above 200°C. When heated to decomposition it emits toxic fumes of NOx. See also m-NITROANILINE, p-NITROANILINE, and ANILINE DYES. 

Chemical reactions that release energy to the surroundings are described as exothermic. In an exothermic reaction the temperature of the surroundings increases. For example, when magnesium reacts with sulfuric acid in a test tube, the energy released is transferred to the surroundings and the temperature of the reaction mixture in the tube increases. 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

The problem involves 2 reactions. Both calcium carbonate and magnesium carbonate react with sulfuric acid. The stoichiometric equations are... 

In the case of a still less reactive halide, or one with a tendency to undergo dehydrohalogenation, it is advantageous to add a reactive halide such as 1-bromo-naphthalene or n-butyl bromide for entrainment. Thus the reaction of 0.05 mole of eyclohexyl chloride and 0.05 mole of 1-bromonaphthalene with 0.33 g. atom of magnesium and isopropanol (0.3 mole) in 50 + 20 ml. of decalin afforded a mixture of 83% of cyclohexane and 10% of cyclohexene (removable with sulfuric acid). By this procedure cyclohexyl fluoride gives cyclohexane (33%) and benzotrifluoride gives toluene (10%). Fluorobenzene is inert. 

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