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Ch.16 - Aqueous Equilibria: Acids & Bases
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.16 - Aqueous Equilibria: Acids & BasesProblem 40
Chapter 16, Problem 40

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

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Step 1: Understand that the strength of a binary acid (an acid that contains hydrogen and one other nonmetal) is determined by the polarity of the H-X bond and the stability of the X- ion. The more polar the bond and the more stable the ion, the stronger the acid.
Step 2: Look at the periodic table. Sulfur (S), selenium (Se), chlorine (Cl), and bromine (Br) are all in the same group (Group 16 and Group 17), but they are in different periods. As you move down a group in the periodic table, the size of the atoms increases.
Step 3: Consider the polarity of the H-X bond. The difference in electronegativity between hydrogen and the other element determines the polarity of the bond. Hydrogen has an electronegativity of 2.1. Chlorine (3.0) and bromine (2.8) have higher electronegativities than sulfur (2.5) and selenium (2.4), so HCl and HBr are more polar than H2S and H2Se.
Step 4: Consider the stability of the X- ion. As you move down a group in the periodic table, the size of the atoms increases, which makes the negative charge of the ion more spread out and the ion more stable. Therefore, H2Se and H2S are more stable than HCl and HBr.
Step 5: Combine the information from steps 3 and 4. The strongest acid will be the one with the most polar bond and the most stable ion. The weakest acid will be the one with the least polar bond and the least stable ion. Therefore, HBr is the strongest acid and H2S is the weakest acid.

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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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Related Practice
Textbook Question

The following pictures represent solutions of three salts NaA (A- = X-, Y-, or Z-); water molecules and Na+ ions have been omitted for clarity.

(b) Which A- anion has the strongest conjugate acid?

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Textbook Question

The following pictures represent solutions of three salts NaA (A- = X-, Y-, or Z-); water molecules and Na+ ions have been omitted for clarity.

(a) Arrange the three A- anions in order of increasing base strength.

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Textbook Question

The following pictures represent aqueous solutions of three acids HA1A = X, Y, or Z2; water molecules have been omitted for clarity.

(e) What is the percent dissociation in the solution of HZ?

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Textbook Question

The following pictures represent aqueous solutions of three acids HA1A = X, Y, or Z2; water molecules have been omitted for clarity.

(c) Which acid, if any, is a strong acid?

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Textbook Question

Which of the following pictures represents a solution of a weak diprotic acid, H2A? (Water molecules have been omitted for clarity.) Which pictures represent an impossible situation? Explain.

(a) (b) (c) (d)

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Textbook Question

A 40.0 mL sample of a mixture of HCl and H3PO4 was titrated with 0.100 M NaOH. The first equivalence point was reached after 88.0 mL of base, and the second equivalence point was reached after 126.4 mL of base.

(e) Sketch the pH titration curve, and label the buffer regions and equivalence points.

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