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Justify the continued use of the Arrhenius definition of acids and bases, despite the development of the more sophisticated Brönsted–Lowry definition - HSC - SSCE Chemistry - Question 29 - 2011 - Paper 1
Question 29
Justify the continued use of the Arrhenius definition of acids and bases, despite the development of the more sophisticated Brönsted–Lowry definition. Why does the ... show full transcript
Worked Solution & Example Answer:Justify the continued use of the Arrhenius definition of acids and bases, despite the development of the more sophisticated Brönsted–Lowry definition - HSC - SSCE Chemistry - Question 29 - 2011 - Paper 1
Step 1
Justify the continued use of the Arrhenius definition of acids and bases, despite the development of the more sophisticated Brönsted–Lowry definition.
Answer
The Arrhenius definition of acids and bases has been foundational in the study of acid-base chemistry, and its continued use is justified for several reasons:
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Simplicity and Clarity: The Arrhenius definition is straightforward, categorizing acids as substances that increase the concentration of hydrogen ions (H⁺) in solution, and bases as those that increase the concentration of hydroxide ions (OH⁻). This simplicity makes it accessible for beginners in chemistry.
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Practical Applications: Many practical laboratory and industrial processes rely on the Arrhenius definitions. For instance, in titrations and reaction calculations, the straightforward relation to H⁺ and OH⁻ ion concentration allows for practical applications in many educational and professional settings.
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Foundation for Advanced Concepts: Understanding the Arrhenius definitions provides a necessary groundwork for more complex theories like Brönsted–Lowry and Lewis theories. These advanced concepts, which involve proton transfer and electron pair donation, build on the foundational ideas present in the Arrhenius definitions.
Overall, while the Brönsted–Lowry definition offers a more comprehensive framework, the utility, clarity, and foundational nature of the Arrhenius definition justify its continued relevance in both educational contexts and real-world applications.
Step 2
Why does the neutralisation of any strong acid in an aqueous solution by any strong base always result in a heat of reaction of approximately –57 kJ mol⁻¹?
Answer
The neutralisation of a strong acid by a strong base results in a consistent heat of reaction of approximately –57 kJ mol⁻¹ due to the formation of water from H⁺ ions and OH⁻ ions. This energy change is representative of the enthalpy of neutralisation, which reflects the energy released when water is formed in this reaction.
The high degree of ionization of both strong acids and strong bases means that the reaction can be effectively considered as a combination of H⁺ and OH⁻ ions to form water. Since this reaction is highly exothermic, the value of –57 kJ mol⁻¹ is a reliable approximation across various strong acid and strong base combinations.