Rank the following anions in order of increasing basicity: Cl^-, OH^-, F^-, and NO_3^-.

• A. NO_3^- < Cl^- < F^- < OH^-
• B. F^- < Cl^- < NO_3^- < OH^-
• C. Cl^- < NO_3^- < OH^- < F^-
• D. OH^- < F^- < Cl^- < NO_3^-

Answer: (A)

Verified step by step guidance

1. Understand that basicity of an anion is related to its ability to accept a proton (H^+), which depends on the strength of its conjugate acid. The weaker the conjugate acid, the stronger the base.
2. Identify the conjugate acids of each anion: Cl^- comes from HCl, OH^- from H2O, F^- from HF, and NO_3^- from HNO_3.
3. Recall the acid strengths (pKa values) of these conjugate acids: HCl and HNO_3 are strong acids (very low pKa), HF is a weak acid (higher pKa), and H2O is very weakly acidic (even higher pKa).
4. Use the relationship that the stronger the acid, the weaker its conjugate base. Therefore, NO_3^- and Cl^- (from strong acids) are weak bases, while F^- and OH^- (from weaker acids) are stronger bases.
5. Rank the anions from least basic to most basic by comparing their conjugate acid strengths: NO_3^- < Cl^- < F^- < OH^-.