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Reactions of barium hydroxide with ammonium salts are strongly endothermic. The reaction of barium hydroxide octahydrate with ammonium chloride [18] [19] or [20] ammonium thiocyanate [20] [21] is often used as a classroom chemistry demonstration, producing temperatures cold enough to freeze water and enough water to dissolve the resulting mixture.
The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion or other chemical reaction. Thermal decomposition is a chemical reaction where heat is a ...
An endothermic process may be a chemical process, such as dissolving ammonium nitrate (NH 4 NO 3) in water (H 2 O), or a physical process, such as the melting of ice cubes. [5] The opposite of an endothermic process is an exothermic process, one that releases or "gives out" energy, usually in the form of heat and sometimes as electrical energy. [1]
In thermochemistry, a thermochemical equation is a balanced chemical equation that represents the energy changes from a system to its surroundings. One such equation involves the enthalpy change, which is denoted with Δ H {\displaystyle \Delta H} In variable form, a thermochemical equation would appear similar to the following:
Ammonium chloride is an inorganic chemical compound with the chemical formula N H 4 Cl, also written as [NH 4]Cl. It is an ammonium salt of hydrogen chloride . It consists of ammonium cations [NH 4 ] + and chloride anions Cl − .
Metathesis reactions can occur between two inorganic salts when one product is insoluble in water. For example, the precipitation of silver chloride from a mixture of silver nitrate and cobalt hexammine chloride delivers the nitrate salt of the cobalt complex: 3 AgNO 3 + [Co(NH 3) 6]Cl 3 → 3 AgCl + [Co(NH 3) 6](NO 3) 3
Some chemistry textbooks [3] as well as the widely used CRC Handbook of Chemistry and Physics [4] define lattice energy with the opposite sign, i.e. as the energy required to convert the crystal into infinitely separated gaseous ions in vacuum, an endothermic process. Following this convention, the lattice energy of NaCl would be +786 kJ/mol.
The Van 't Hoff equation relates the change in the equilibrium constant, K eq, of a chemical reaction to the change in temperature, T, given the standard enthalpy change, Δ r H ⊖, for the process. The subscript r {\displaystyle r} means "reaction" and the superscript ⊖ {\displaystyle \ominus } means "standard".