Choosing the Stronger Acid: HOCl or HClO₂, H₂SeO₄ or H₂SeO₃

What are the factors that determine the strength of acids in each pair? The strength of an acid is determined by the stability of its conjugate base. The stronger the acid, the weaker its conjugate base. In the case of oxoacids, the number of oxygen atoms attached to the central element plays a crucial role in determining acidity.

When comparing acids with similar central elements, such as chlorine in the case of HOCl and HClO₂, the acid with more oxygen atoms is generally stronger. This is because the additional oxygen atoms help in stabilizing the negative charge on the conjugate base after losing a proton.

For example, in the pair of oxoacids HOCl and HClO₂, HClO₂ is the stronger acid. This is due to the fact that the conjugate base of HClO₂, ClO₂-, is more stable than the conjugate base of HOCl, ClO-.

Similarly, when comparing H₂SeO₄ and H₂SeO₃, which contain selenium as the central element, the acid with more oxygen atoms (H₂SeO₄) is stronger. The additional oxygen atoms in H₂SeO₄ lead to a higher oxidation state for selenium, resulting in enhanced acid strength.

Conclusion:

Understanding the principles of acid-base equilibria and the properties of oxoacids and their corresponding elements is crucial in determining the strength of acids. Factors such as the number of oxygen atoms attached to the central element play a significant role in predicting acid strength.

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