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The decahydrate is formed from water solutions crystallizing in the temperature range −2.1 to +32.0 °C, the heptahydrate in the narrow range 32.0 to 35.4 °C and above this temperature the monohydrate forms. [13] In dry air the decahydrate and heptahydrate lose water to give the monohydrate.
Sodium percarbonate or sodium carbonate peroxide is a chemical substance with empirical formula Na 2 H 3 C 2 O 6. It is an adduct of sodium carbonate ("soda ash" or "washing soda") and hydrogen peroxide (that is, a perhydrate ) whose formula is more properly written as 2 Na 2 CO 3 · 3 H 2 O 2 .
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Another example of thermal decomposition is 2Pb(NO 3) 2 → 2PbO + O 2 + 4NO 2. Some oxides, especially of weakly electropositive metals decompose when heated to high enough temperature. A classical example is the decomposition of mercuric oxide to give oxygen and mercury metal.
The tables below provides information on the variation of solubility of different substances (mostly inorganic compounds) in water with temperature, at one atmosphere pressure. Units of solubility are given in grams of substance per 100 millilitres of water (g/100 ml), unless shown otherwise.
The release of carbon dioxide gas from the reaction mixture drives the reaction to completion. For example, a common, science-fair "volcano" reaction involves the reaction of hydrochloric acid with sodium carbonate: 2 HCl + Na 2 CO 3 → H 2 CO 3 + 2 NaCl H 2 CO 3 → H 2 O + CO 2
A key step in this process is the reduction of sodium sulfate with coal: [3] Na 2 SO 4 + 2 C → Na 2 S + 2 CO 2. The Na 2 S is then treated with calcium carbonate to give sodium carbonate, a commodity chemical. Recently, development of the 'MagSonic' carbothermic magnesium process has restarted interest in its chemistry: [4] MgO + C ↔ Mg + CO
Sodium oxalate starts to decompose above 290 °C into sodium carbonate and carbon monoxide: [2]. Na 2 C 2 O 4 → Na 2 CO 3 + CO. When heated at between 200 and 525°C with vanadium pentoxide in a 1:2 molar ratio, the above reaction is suppressed, yielding instead a sodium vanadium oxibronze with release of carbon dioxide [6]