What is meant by the conjugate acid-base pair? Find the conjugate acid`//`base for the following species:
`HNO_(2), CN^(Θ), HClO_(4), F^(Θ), overset(Θ)(O)H, CO_(3)^(2-)`, and `S^(2-)`

Explanation

To solve the question regarding conjugate acid-base pairs, we will first define what a conjugate acid-base pair is and then identify the conjugate acids or bases for the given species.

### Step-by-Step Solution:

1. **Definition of Conjugate Acid-Base Pair:**
A conjugate acid-base pair consists of two species that differ by the presence or absence of a proton (H⁺). When an acid donates a proton, it forms its conjugate base. Conversely, when a base accepts a proton, it forms its conjugate acid.

2. **Finding Conjugate Pairs:**
We will analyze each species provided in the question to identify their conjugate acids or bases.

- **For HNO₂ (Nitrous Acid):**
- HNO₂ can donate a proton (H⁺) to form NO₂⁻ (Nitrite Ion).
- **Conjugate Base:** NO₂⁻

- **For CN⁻ (Cyanide Ion):**
- CN⁻ can accept a proton (H⁺) to form HCN (Hydrogen Cyanide).
- **Conjugate Acid:** HCN

- **For HClO₄ (Perchloric Acid):**
- HClO₄ can donate a proton (H⁺) to form ClO₄⁻ (Perchlorate Ion).
- **Conjugate Base:** ClO₄⁻

- **For F⁻ (Fluoride Ion):**
- F⁻ can accept a proton (H⁺) to form HF (Hydrofluoric Acid).
- **Conjugate Acid:** HF

- **For OH⁻ (Hydroxide Ion):**
- OH⁻ can accept a proton (H⁺) to form H₂O (Water).
- **Conjugate Acid:** H₂O

- **For CO₃²⁻ (Carbonate Ion):**
- CO₃²⁻ can accept a proton (H⁺) to form HCO₃⁻ (Bicarbonate Ion).
- **Conjugate Acid:** HCO₃⁻

- **For S²⁻ (Sulfide Ion):**
- S²⁻ can accept a proton (H⁺) to form HS⁻ (Hydrogen Sulfide Ion).
- **Conjugate Acid:** HS⁻

### Summary of Conjugate Acid-Base Pairs:
- HNO₂ → NO₂⁻ (Conjugate Base)
- CN⁻ → HCN (Conjugate Acid)
- HClO₄ → ClO₄⁻ (Conjugate Base)
- F⁻ → HF (Conjugate Acid)
- OH⁻ → H₂O (Conjugate Acid)
- CO₃²⁻ → HCO₃⁻ (Conjugate Acid)
- S²⁻ → HS⁻ (Conjugate Acid)