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Ch.16 - Aqueous Equilibria: Acids & Bases
Chapter 16, Problem 40

Locate sulfur, selenium, chlorine, and bromine in the periodic table: (a) Which binary acid 1H2S, H2Se, HCl, or HBr2 is the strongest? Which is the weakest? Explain.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Binary Acids

Binary acids are compounds consisting of hydrogen and one other nonmetal element. They are named using the prefix 'hydro-' followed by the root of the nonmetal's name and the suffix '-ic.' The strength of binary acids generally increases with the size of the nonmetal atom, as larger atoms can stabilize the negative charge of the conjugate base more effectively.
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Acid Strength and Electronegativity

The strength of an acid is influenced by the electronegativity of the nonmetal atom bonded to hydrogen. As electronegativity increases, the bond between hydrogen and the nonmetal becomes stronger, making it harder for the acid to donate a proton (H+). Therefore, acids formed with less electronegative elements tend to be stronger, as they can more readily release protons.
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Periodic Trends

Periodic trends refer to the predictable patterns observed in the periodic table, such as atomic size, ionization energy, and electronegativity. As you move down a group in the periodic table, atomic size increases, and electronegativity decreases. This trend helps in predicting the strength of binary acids, as larger atoms (like sulfur and selenium) form stronger acids compared to smaller, more electronegative atoms (like chlorine).
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