key term - CN⁻/HCN

Definition

CN⁻ (cyanide ion) and HCN (hydrogen cyanide) are part of a conjugate acid-base pair, where HCN acts as the Brønsted-Lowry acid and CN⁻ functions as its conjugate base. In this relationship, HCN can donate a proton (H⁺) to become CN⁻, highlighting the reversible nature of acid-base reactions. Understanding this pair is essential for grasping concepts related to acidity, basicity, and equilibrium in chemical reactions.

5 Must Know Facts For Your Next Test

1. HCN is a weak acid with a low dissociation constant, meaning it does not completely dissociate in water, while CN⁻ is its corresponding conjugate base.
2. The equilibrium between HCN and CN⁻ is influenced by pH; as the pH increases, the concentration of CN⁻ increases due to the decreased availability of protons.
3. Cyanide is highly toxic because it inhibits cellular respiration by binding to cytochrome c oxidase, making it important to understand the properties of HCN and CN⁻ in safety contexts.
4. The reaction between HCN and CN⁻ can be represented as: $$ ext{HCN} ightleftharpoons ext{H}^+ + ext{CN}^-$$, demonstrating the dynamic nature of acid-base interactions.
5. In biological systems, the presence of HCN can lead to severe physiological effects due to its interference with oxygen utilization in tissues.

Review Questions

• How does the Brønsted-Lowry theory help explain the relationship between HCN and CN⁻?
  • The Brønsted-Lowry theory illustrates that HCN functions as a Brønsted-Lowry acid by donating a proton (H⁺) to form its conjugate base, CN⁻. This concept emphasizes the reversible nature of their relationship, where HCN can easily convert to CN⁻ in an equilibrium reaction. This pairing demonstrates the fundamental idea of acid-base interactions and how substances can switch roles depending on the environment.
• In what ways do changes in pH affect the equilibrium between HCN and CN⁻?
  • Changes in pH significantly impact the equilibrium between HCN and CN⁻ because an increase in pH means there are fewer protons available in solution. As a result, more HCN will dissociate into CN⁻ and H⁺ ions. Conversely, lowering the pH leads to an increase in H⁺ concentration, which pushes the equilibrium back towards forming more HCN from CN⁻. This dynamic illustrates how pH directly influences the acid-base behavior of these species.
• Evaluate the implications of cyanide toxicity in relation to its chemistry as an acid-base pair.
  • Cyanide's toxicity is closely linked to its chemistry as an acid-base pair. When HCN enters biological systems, it can disrupt cellular respiration by binding to enzymes essential for oxygen utilization. Understanding this behavior within the framework of acid-base chemistry highlights why both forms, HCN and CN⁻, are critical when assessing environmental and health risks. Additionally, it underscores the importance of studying conjugate pairs like these to comprehend their broader physiological impacts.

Related terms

Brønsted-Lowry Acid: A substance that donates a proton (H⁺) in a chemical reaction.

Brønsted-Lowry Base:

A substance that accepts a proton (H⁺) in a chemical reaction.

Equilibrium Constant (K): A value that expresses the ratio of products to reactants at equilibrium for a reversible reaction.