Ammonium nitrate, dissolving

The Bachmann process, used in the United States and in some European countries, is a simplification of a series of complex reactions. In this process, a solution of one part hexamine in 1.65 parts acetic acid, and a solution of 1.50 parts ammonium nitrate dissolved in 2.0 parts nitric acid and 5.20 parts acetic anhydride are used. The reaction may be summarized as ... 

To see where a thermochemical equation comes from, consider the process by which ammonium nitrate dissolves in water ... 

We can therefore report that AH = —208 kj because the enthalpy of the reaction mixture decreases by 208 kj in this reaction (Fig. 6.18). An endothermic process absorbs heat, and so when ammonium nitrate dissolves in water the enthalpy of the system increases (Fig. 6.19). Note that AH < 0 for exothermic reactions, whereas AH > 0 for endothermic reactions. 

When a salt containing polyatomic ions dissolves In water, the cations separate from the anions, but each polyatomic ion remains intact. An example Is ammonium nitrate, composed of NH4 polyatomic cations and NO3 polyatomic anions. Ammonium nitrate dissolves In water to give a solution containing NH4 cations and NO3 anions, as Figure 3-21 Illustrates. 

We are asked to find q and determine its sign for ammonium nitrate dissolving in water. 

Initiation with only one portion of ceric amnoniiM nitrate (rather than with two portions added one hour apart) reduces both the conversion of monomer to polymer and the water absorbency of the fined product. Based on these results, starch in future reactions was gelatinized by heating for 60 min at 95 C, to more closely simulate conditions of continuous steam jet cooldng 02) r %diich would be used commercially. Also, polymerizations were initiated with two portions of ceric ammonium nitrate dissolved in IH HNQs, seponification mixtures were stirred continuously rather than intermitt Ttly (as a matter of convenience), and absorbent polymers were dried at 40 C. 

Dissolving is often an endothermic process. For example, when ammonium nitrate dissolves in water the temperature of the water falls, indicating that energy is being taken from the surroundings. Photosynthesis and thermal decomposition are other examples of endothermic processes. 

C) Commercial instant ice packs are available that contain a mixture of ammonium nitrate and water separated by a barrier. When the ice pack is twisted, the barrier breaks and the two substances mix. The temperature rapidly decreases as the ammonium nitrate dissolves in the water. Describe the changes in enthalpy, entropy, and free energy during this process. 

C) Because the temperature decreases, the process is endothermic. Therefore, AH > 0. The ammonium nitrate dissolves in the water so the entropy increases (AS > 0). The process occurs spontaneously, which means that AG must be negative. 

Ammonium nitrate dissolves readily in water in addition, the salt is hygroscopic. Therefore, care must be taken to avoid moisture during transportation and storage. When the salt dissolves in water, heat is absorbed (A // = 26 kJ mol ). Therefore, ammonium nitrate can be used in freezing mixtures, for example, in mixtures with sodium chloride and ice. 

As you observed in the DISCOVERY LAB at the beginning of this chapter, some solutions release energy as they form, whereas others absorb energy during formation. For example, after ammonium nitrate dissolves in water, its container feels cool. In contrast, after calcium chloride dissolves in water, its container feels warm. You will learn more about the heat of solution in the next chapter. 

Heat is absorbed when ammonium nitrate dissolves in water in a cold pack. In this photograph, heat is transferred from the injured knee to the chemical process. 

Ammonium nitrate dissolves in water according to the reaction... 

The heavy plastic cold pack holds ammonium nitrate and water. The two substances are separated by a plastic divider. When you squeeze the bag, you break the divider so that the ammonium nitrate dissolves in the water. The dissolving process absorbs heat energy, which must come from the surrounding environment—the surrounding air or your skin after you place the pack on the injury. 

The excess ammonium nitrate dissolves in the water produced in the reaction, (b) The dissolution process is very endothermic. If the flask is placed on a wet wooden block, the water freezes and attaches the block to the flask. 

Peroxotungstic acids like H2WO6 or H2W2O11 can be exhacted from nitrate solutions into trialkyl-(C7-C9)-benzyl ammonium nitrate dissolved in trichloroethe-lyne. 

Instant hot and cold packs create aqueous solutions that form exothermically or endothermically and therefore release or absorb heat. A hot pack generates heat when a salt such as calcium chloride dissolves in water that is stored in the pack. The calcium chloride dissolves exothermically. A cold pack absorbs heat when a salt such as ammonium nitrate dissolves in water. The ammonium nitrate dissolves endothermically. 

Ammonium nitrate dissolves amazingly well in water. It dissolves so well that on a humid day it will suck water out of the air and dissolve itself, forming a wet puddle. It doesn t dissolve very well in ethyl alcohol, the denatured alcohol found in the paint section of the hardware store. Urea, on the other hand dissolves well in both water and alcohol. This will form the basis of our isolation procedure. 

The ice packs consist of a thin plastic bag containing water, which is contained in a larger outer bag containing ammonium nitrate. When the pack is thumped, the bag containing the water breaks and the ammonium nitrate dissolves in the water. Ammonium nitrate is used because when it dissolves, heat is taken in... 

Ammonium nitrate dissolves spontaneously and endother-mally in water at room temperature. What can you deduce about the sign of A5 for this solution process ... 

When a 3.88-g sample of sohd ammonium nitrate dissolves in 60.0 g of water in a coffee-cup calorimeter (Figure 5.18), the temperature drops from 23.0°C to 18.4 C. Calculate AH (in kJ/mol NH4NO3) for the solution process... 

Ammonium nitrate (NH4NO3) dissolves in water with an endothermic heat of reaction of 26.4 kJ mol. How much ambient heat will be absorbed when 2.0 kg of ammonium nitrate dissolves in water (This reaction is utilized in instant ice packs for treating injuries. Solid ammonia nitrate is contained inside a thin-walled plastic bag, which is sealed inside a thicker bag that also contains some water. The inner bag can be broken by pressing the outer bag, thereby allowing the ammonium nitrate to form a solution with the water which gets quite cold.)... 

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