Reactions between the liquid alkali-metals and liquid water

Ashworth, Allan B. (1979) Reactions between the liquid alkali-metals and liquid water. PhD thesis, University of Nottingham.

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Abstract

The rates of reaction of the constituents of sodium-potassium alloy with water have been determined in the temperature range 20 - 600C. They fall into two categories; the first is applicable to the instant the alloy meets the water, and the second applies to reaction of the metal through a bubble of hydrogen. The rates are widely different for these two stages, yet the activation energies are similar, being 38.3 and 33.0 KJ/mole respectively for sodium, and 24.5 and 27.3 KJ/mole respectively for potassium. The rate of reaction of sodium alone at 30 C, has also been determined.

The behaviour of liquid metals when injected into water has been studied by high speed photography. Such jets disintegrate, after a short distance of travel, into small globules, each contained within a hydrogen gas bubble. These globules then travel upwards through water and consequently react much more slowly.

The reaction rate may be reduced by the addition of small concentrations of mineral acids to the water, due to the, formation of salts at the metal-water interface which are less soluble than sodium hydroxide. Strong solutions of acid however, increase the rate of reaction. The addition of hydroxide ions as NH4OH has little effect on the rates.

The metals undergo secondary reaction in that the hydrogen which is initially formed subsequently reacts with the metal to produce hydrides. These are eventually hydrolysed.

The most probable reaction intermediate in the solution phase of the reaction is the solvated electron, e - (sq)' which has been detected photographically due to its absorption of light in the visible region of the spectrum.

Overall reaction mechanisms for both reaction in solution and reactions at the metal surface have been proposed.

Item Type:Thesis (PhD)
Supervisors:Pulham, R.J.
Halstead, W.D.
Faculties/Schools:UK Campuses > Faculty of Science > School of Chemistry
ID Code:1481
Deposited By:Mrs Olga Lashkova
Deposited On:02 Aug 2010 11:02
Last Modified:02 Aug 2010 11:02

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