New answers tagged

0

The operation of light emitting diodes involves the electrochemical creation of radical - cations and -anions that upon recombination lead to molecules in their emitting excited states. The formation of the above charged species happen when the applied forward potential is positive enough to inject (reduction) electrons from the cathode to the LUMO of the ...


0

No. Neither ferrous, nor non-ferrous metals can be hardened by tempering. Tempering generally refers to steel and it does the opposite of hardening. It reduces the hardness and brittleness of the steel (softens it) while improving the toughness and making it more ductile. This makes the steel better able to handle further cold processing and makes it more ...


0

No. Neither ferrous, nor non-ferrous metals can be hardened by tempering. Tempering generally refers to steel and it does the opposite of hardening. It reduces the hardness and brittleness of the steel (softens it) while improving the toughness and making it more ductile. This makes the steel better able to handle further cold processing and makes it more ...


2

Research notes in this ACS article Kinetics of Hydrogen Reduction of Manganese Dioxide that even heating $\ce{MnO2}$ in an atmosphere of hydrogen gas only results in $\ce{MnO}$. The source further notes that very high temperatures (some 1,600 K) are required for any appreciable formation of the metal. As such, a more facile approach, simply dissolve the ...


6

You may heat mixture of $\ce{MnO2}$ with charcoal to higher than $\pu{850 °C},$ in the absence of air. Manganese will be produced in the solid state by reduction of the oxide. But it is sensitive to air oxidation and easily reoxidized. So better use an excess of charcoal. In the industry, rough $\ce{MnO2}$ out of the mine is first reduced to $\ce{MnO}$ by $\...


3

The reaction $$\ce{Al2O3 + 3 Mg -> 3 MgO + 2 Al}$$ is slightly exothermic, with a $\Delta H = - 130 kJ/mol$. It is also exoergic at all reasonable temperatures, as $\Delta S $ is very small ($- 1.5 J/mol$). So the reaction is in principle feasible. The trouble is that $\ce{Al2O3}$ and $\ce{Mg}$ are solid at room temperature. And the reactions between ...


1

The stability of the various iron oxides depends on the oxygen fugacity (or oxygen partial pressure, which is a good approximation to fugacity in near-atmospheric pressures). $\ce{Fe^3+}$ is the stable form of iron in atmospheric oxygen partial pressures, this in such conditions $\ce{Fe2O3}$ (hematite) will always be the stable product. The lower oxidation ...


Top 50 recent answers are included