Which of each pair of acids is stronger? Why? (a) GeH4, AsH3 (b) HNO2, HNO3

Name: Problem 102, Chapter 15: Chemistry Principles and Practice
Uploaded: 2022-02-20T23:54:55-08:00
Duration: 2 min 8 s
Channel: Adriano Chikande
Description: Which of each pair of acids is stronger? Why? (a) GeH4, AsH3 (b) HNO2, HNO3

step 1 In this question we've been given some pairs of acids and we've been asked to determine which of

Which of each pair of acids is stronger? Why? (a) GeH4, AsH3...

Key Concepts

Acid Strength and pKa

Acid strength refers to the tendency of a compound to donate a proton (H+). In quantitative terms, this is often indicated by the compound's pKa value, with lower pKa values corresponding to stronger acids. The strength of an acid depends largely on how readily it can release a proton, which in turn is influenced by the bond strength between the hydrogen and the rest of the molecule and the stability of the species formed after deprotonation.

Conjugate Base Stability

The stability of an acid’s conjugate base is a critical factor in determining acid strength. A more stable conjugate base better accommodates the negative charge left behind after proton loss, which shifts the equilibrium in favor of deprotonation. Factors that stabilize a negative charge include polarizability, delocalization, and the inductive effects of electronegative substituents.

Resonance Stabilization in Oxyacids

In oxyacids such as HNO2 and HNO3, resonance stabilization plays a key role. The nitrate ion (NO3–) formed from HNO3 has more resonance structures and a greater delocalization of the negative charge compared to the nitrite ion (NO2–) formed from HNO2. This enhanced resonance stabilization renders HNO3 a stronger acid because its conjugate base is lower in energy and more stable.

Molecular Structure Effects in Covalent Hydrides

For binary hydrides like GeH4 and AsH3, molecular structure significantly influences acidity. Factors such as the number of hydrogen atoms bonded to the central atom, the central atom’s electronegativity, and its ability to stabilize a negative charge upon deprotonation determine acid strength. Even small differences in bonding and electron distribution can lead to differences in how easily a proton is removed, making one hydride slightly more acidic than another.

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