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The Columbia Electronic Encyclopedia, 6th ed. Additional Symbols Used in Chemical Equations.The sign = is sometimes used in place of the double arrow. The equation is 2H 2O ⥨H 2O H 3O + + OH −. These ions exist in equilibrium with water molecules. For example, liquid water dissociates to form hydronium ions (H 3O +) and hydroxide ions (OH −). When chemical equilibrium occurs in a reaction, the double arrow ( ⥨ ) is used instead of the single arrow. The formulas AgNO 3, NaCl, and NaNO 3 do not represent molecules, since these substances are almost completely ionized in water solution (see ion). When metal ions combine with the hydroxide ions (OH-) from either sodium hydroxide solution or ammonia solution, they form insoluble precipitates. The H 2O above the arrow shows that the reaction takes place in the presence of water-in this case, in water solution. When a precipitate is formed by a reaction, the substance that precipitates is often followed by a downward-pointing arrow, e.g., AgNO 3 + NaCl →H 2O AgCl↓ + NaNO 3. naga, 190 peace gesture, 158 peacock, 190 Pegasus, 125 percent sign, 237 Powder symbol, 21 prayer flags, 184 prayer gesture, 156 Precipitate symbol. The upward-pointing arrow after the O 2 indicates that this product is gaseous and escapes.

M g ( O H) 2 ( s) + 2 H C l M g C l 2 + 2 H 2 O ( l) A precipitation reaction is a kind of chemical reaction in which two soluble salts in a fluid solution mixes and one of the items is an insoluble. Option Terms for the Motherlode Project: The Company entered into two underlying property option agreements granting Precipitate the exclusive right to earn a 100 interest in a combined 6,100. The Greek letter delta under the arrow represents the heating. Some more examples of precipitation reaction with their chemical equations are given below: A g N O 3 + N a C l A g C l + N a N O 3. For example, when mercuric oxide is heated it decomposes into mercury metal and oxygen gas this reaction is shown by the equation 2HgO →Δ 2Hg + O 2↑. A symbol written above or below the reaction arrow indicates special reaction conditions. There are a number of other symbols used in chemical equations.
