Barium hydroxide thiocyanate

Baryum, n. barium, -chlorhydrat, n. barium chloride. -hydrat, n. barium hydroxide, -hyperoxyd, n. barium peroxide, barium dioxide. -jodid, n. barium iodide, -lack, m. barium lake, -oxydhydrat, n. barium hydroxide. -platincyaniir, n. barium cyano-platinite, barium cyanoplatinate(II). -rho-danid, n. barium thiocyanate, -salz, n. bar ium salt. 

FIGURE 6.9 The endothermic reaction between ammonium thiocyanate, NH4SCN, and barium hydroxide octahydrate, Ba(0H)2-8H20, absorbs a lot of heat and can cause water vapor in the air to freeze on the outside of the beaker. 

A favourable endothermic reaction occurs when barium hydroxide is mixed with ammonium thiocyanate. If you removed the stopper in photograph (B), you would detect the characteristic odour of ammonia. 

Certainly many favourable physical and chemical changes are exothermic. Some favourable changes, however, involve no release of energy. Others are actually endothermic. For example, a favourable endothermic chemical reaction occurs when barium hydroxide and ammonium thiocyanate are placed in an Erlenmeyer flask, as shown in Figure 7.4. 

Ammonium Formate Ammonium Hydrosulfide Ammonium Molybdate Ammonium Nitrate Ammonium Phosphate, Dibasic Ammonium Phosphate, Monobasic. .. Barium Hydroxide Ammonium Phosphate, Monobasic Ammonium Sulfate Ammonium Sulfide Ammonium Thiocyanate Ammonium Thiosulfate Antimony... 

Derivation By heating barium hydroxide with ammonium thiocyanate and subsequent crystallization. 

When the two compounds ammonium thiocyanate and barium hydroxide octahydrate are mixed, a reaction occurs in which heat is absorbed from the surroundings. The flask becomes so cold that if a film of water is on the bottom of the flask, it will freeze the flask to a wooden block. 

FIGURE 5.8 Endothermic and exothermic reactions, (a) When ammonium thiocyanate and barium hydroxide octahydrate are mixed at room temperature, the temperature drops, (b) The reaction of powdered aiummum with Fe203 (the thermite reaction) proceeds vigorousiy, reieasing heat and forming Ai203 and moiten iron. 

Perhaps you have seen a demonstration of the endothermic but favorable reaction of barium hydroxide and ammonium thiocyanate. This reaction absorbs so much heat from its surroundings that it can freeze water in contact with the reaction flask (Figure 8.10) ... 

FIGURE 8.10 A favorable but endothermic reaction. The reaction of barium hydroxide and ammonium thiocyanate is one of the uncommon examples of a favorable reaction that absorbs heat from its surroundings. 

Barium thiocyanate was first prepared by Berzelius, who roasted barium hexacyanoferrate(II) with sulfur. It has also been obtained by reaction of barium carbonate with a solution of thiocyanic acid, by conversion of ammonium thiocyanate through the copper (I) thiocyanate by consecutive reactions with copper(I) chloride and barium hydroxide, by treatment of Prussian blue with barium sulfide, and by reaction of barium sulfide, sulfur, and cyanamide. The procedure described below makes possible the preparation of barium thiocyanate in any desired quantity from barium hydroxide and ammonium thiocyanate as starting materials. The 3-hydrate, " which is obtained first, is dehydrated readily to yield anhydrous barium thiocyanate. 

The acid-base chemistry reaction of barium hydroxide (Ba(OH)2) with ammonium thiocyanate (NH SCN) in water creates barium thiocyanate, ammonia, and water. The reaction is highly favorable, but is also so endothermic that the solutions cools to such an extent that a layer of frost forms on the reaction vessel. Explain how an endothermic reaction can be favorable. 

Ammonium hydrogen phosphate Ammonium nitrate Ammonium phosphate Ammonium sulfate Ammonium sulfide Ammonium thiocyanate Arsenic acid Barium carbonate Barium chloride Barium hydroxide Barium nitrate Barium sulfate Barium sulfide Battery acid Beryllium chloride Beryllium sulfate Boracic acid... 

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