Arrange the following in decreasing order of basic strenth.
`underset(I)(CI^(-)) underset(II)(RCOO^(-)) underset(III)(OH^(-)) underset(IV)(RO^(-)) underset(V)(NH^(-))`

Options

A. `IgtIIltIIIgtIVltV`
B. `VgtIVgtIIgtIIIgtI`
C. `IgtIIgtIIIgtIVgtV`
D. `VgtIVgtIIIgtIIgtI`

Answer

To arrange the given anions in decreasing order of basic strength, we need to analyze the basicity of each ion based on their structure and the electronegativity of the atoms involved. The ions we need to consider are:

1. \( \text{Cl}^- \) (Chloride ion)
2. \( \text{RCOO}^- \) (Carboxylate ion)
3. \( \text{OH}^- \) (Hydroxide ion)
4. \( \text{RO}^- \) (Alkoxide ion)
5. \( \text{NH}_2^- \) (Amide ion)

### Step 1: Understand Basicity
Basicity is the ability of a species to accept protons (H⁺ ions). The stronger the base, the more readily it accepts protons. Basicity is influenced by the electronegativity of the atom that carries the negative charge and the stability of the resulting species after protonation.

### Step 2: Analyze Each Ion
1. **\( \text{NH}_2^- \)**: The amide ion has a nitrogen atom, which is less electronegative than oxygen. Therefore, it can donate its lone pair of electrons readily, making it a strong base.

2. **\( \text{RO}^- \)**: The alkoxide ion also has a negatively charged oxygen atom, which is less electronegative than nitrogen. This makes it a strong base, but not as strong as the amide ion.

3. **\( \text{OH}^- \)**: The hydroxide ion is a strong base but is less basic than the alkoxide ion due to the higher electronegativity of oxygen compared to nitrogen.

4. **\( \text{RCOO}^- \)**: The carboxylate ion has resonance stabilization, which makes it less basic than hydroxide and alkoxide ions. The negative charge is delocalized over two oxygen atoms, reducing its ability to accept protons.

5. **\( \text{Cl}^- \)**: The chloride ion is the least basic among these ions. Chlorine is highly electronegative, and the negative charge is stable, making it less likely to accept a proton.

### Step 3: Arrange in Decreasing Order of Basic Strength
Based on the analysis above, we can arrange the ions in decreasing order of basic strength as follows:

1. \( \text{NH}_2^- \) (strongest)
2. \( \text{RO}^- \)
3. \( \text{OH}^- \)
4. \( \text{RCOO}^- \)
5. \( \text{Cl}^- \) (weakest)

### Final Order
Thus, the final order of decreasing basic strength is:
\[ \text{NH}_2^- > \text{RO}^- > \text{OH}^- > \text{RCOO}^- > \text{Cl}^- \]