Hydrogen gas formation

Nakashima M, Masaki NM (1996) Radiolytic hydrogen gas formation from water adsorbed on type Y zeolytes. Rad Phys Chem 46 241-245... 

The apparatus should be vented. Hydrogen gas formation causes vigorous bubbling. 

Minor differences between the three electrolyte solutions are also observed. First, electrolyte number 3 only shows a peak maximum in the current-potential curves at potentials higher than 8 V. However, this is very clear because its pH value is smaller, indicating that this electrolyte solution possesses a higher buffer capacity against consumption of hydrogen ions in the vicinity of the fibre surface, avoiding hydrogen gas formation and Ni(OH)2 precipitation. Secondly, at a potential of 4V, no deposition occurred in electrolyte solution number 3, indicated by the absence of an increase in the measured electrical current and confirmed by XPS data. Additionally in this case, the lower pH plays an important role because of the lower pH value, the applied potential difference does not overlap with the potential window in which the reduction of Ni(II) occurs. Therefore no deposition is observed. 

Consider now the fate of some metal ion, such as lead(II), that begins to deposit at point A on the cathode potential curve. Lead(II) would codeposit well before copper deposition was complete and would therefore interfere with the determination of copper. In contrast, a metal ion, such as cobalt(II), that reacts at a cathode potential corresponding to point C on the curve would not interfere because depolarization by hydrogen gas formation prevents the cathode from reaching this potential. 

Problem Diluted adds dissolve active metals and are accompanied by hydrogen gas formation metal sulfate solutions are formed in reactions with diluted sulfuric acid, metal chloride solutions in the case of reactions with hydrochloric acid. Because acids are involved, one tends to jump to the conclusion that it has to be an acid-base reaction (see E7.2). In order to make clear that one is dealing with redox reactions, the following experiments should be interpreted in that sense. 

The anthropogenic H2 is emitted into the air in automotive exhaust gases, which contain H2 in the range of 1-5 % by volume. The nature of the oceanic source is not entirely clear but it is probably due to microbiological activity. However, the supersaturation of ocean waters unambiguously indicates hydrogen gas formation there. The emission from soils is caused by the fermentation of bacteria. 

A promising new area of enzymatic reactions is that of anaerobes. These organisms use redox systems that are not pyridine nucleotide dependent, but can use mcthylvirologen or benzylviologen (commercially available) as mediators. Electron donors can be hydrogen gas, formate, or carbon monoxide rather than glucose." The first new enzyme from this source is a 2-enoatc reductase, effected with stereospecific /rans-addition of hydrogen. An... 

The cells or crude cell extracts which will be described proceed by ways revealed by Schemes 2a and 2b, respectively. Electrons supplied by hydrogen gas, formate, carbon monoxide or the cathode of an electrochemical cell are channelled via an artificial electron mediator such as a reduced viologen (V ) or others to the enzymes reducing... 

Productivity munbers (PN) observed for the reduction of 2-oxo-4-phenyl-(3 )-butenoate in a concentration of 0.1 and 0.2 M using hydrogen gas, formate or their combination. 

Conditions for conversions in a preparative scale (see above) were optimised with 2-oxo-4-phenyl-3-butenoate. Reaction rates depended on pH and reached their maximmn at pH 7 (Fig. 2). Table 12 shows the productivity numbers for the reduction of 0.1 and 0.2 M 2-oxo-4-phenyl-3-butenoate with hydrogen gas, formate or a combination of both... 

Alloying Zn with mercury metal to form an amalgam increases the electrochemical overpotential for hydrogen gas formation oti Zn. Zinc amalgams in the range of 2-15% Hg by weight of Zn were common. 

An overhead projector demonstation employing hydrogen gas formation. Lee R. Summerlin and James L. Ealy, Jr., "Activity Series for Some Metals," Chemical Demonstrations,... 

This conventional beginning is followed by a rather unconventional conclusion, as aromaticity is regained through elimination of hydride (Fig. 14.104).This step is unconventional because loss of hydride from an organic compound is rare. Aminopyridine and potassium hydride are the initially formed products. These react rapidly and irreversibly to form hydrogen gas and a nicely resonance-stabilized amide ion. A final hydrolysis step regenerates aminopyridine. It is presumably the irreversible nature of hydrogen gas formation that helps drive this reaction to completion. 

Figures 11J5 and 11.16 illustrate two designs of Leclanche battery. The first shows the traditional cylindrical design. The negative zinc electrode is a zinc lining to the metal can which is amalgamated with mercury to minimize hydrogen gas formation by reaction of the metal with water the separator is a paper stiffened with cellulose or starch placed adjacent to the zinc can. The positive current collector is a carbon rod at the centre of the can, while most of the volume is taken up by the positive paste. This is a mixture of powdered manganese dioxide ainmotmtm chloride and acetylene black (carbon) to increase the conductivity the pores are filled with an aqueous electrolyte (NH Cl + ZnCl ) gelled by addition of starch. The can is totally scaled.

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