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Ammonia is used in its anhydrous form (a gas) and the nitric acid is concentrated. The reaction is violent owing to its highly exothermic nature. After the solution is formed, typically at about 83% concentration, the excess water is evaporated off to leave an ammonium nitrate (AN) content of 95% to 99.9% concentration (AN melt), depending on ...
For elements that have multiple allotropes, the reference state usually is chosen to be the form in which the element is most stable under 1 bar of pressure. One exception is phosphorus, for which the most stable form at 1 bar is black phosphorus, but white phosphorus is chosen as the standard reference state for zero enthalpy of formation. [2]
Enthalpy change of solution in water at 25 °C for some selected compounds [2] Compound ΔH o in kJ/mol; hydrochloric acid: −74.84 ammonium nitrate +25.69 ammonia: −30.50 potassium hydroxide: −57.61 caesium hydroxide: −71.55 sodium chloride +3.87 potassium chlorate +41.38 acetic acid: −1.51 sodium hydroxide: −44.50
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".
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 In variable form, a thermochemical equation would appear similar to the following:
CaCO 3 → CaO + CO 2 The reaction is used to make quick lime, which is an industrially important product. 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.
For comparison of different reactions, all values of ΔG refer to the reaction of the same quantity of oxygen, chosen as one mole O (1 ⁄ 2 mol O 2) by some authors [2] and one mole O 2 by others. [3] The diagram shown refers to 1 mole O 2, so that e.g. the line for the oxidation of chromium shows ΔG for the reaction 4 ⁄ 3 Cr(s) + O 2 (g ...
A reaction with ∆H°<0 is called exothermic reaction while one with ∆H°>0 is endothermic. Figure 8: Reaction Coordinate Diagrams showing favorable or unfavorable and slow or fast reactions [ 7 ] The relative stability of reactant and product does not define the feasibility of any reaction all by itself.