Among the following, the surfactant that will form micelles in aqueous solution at the lowest molar concentration at ambient condition is

Options

A. `CH_3(CH_2)15N^+(CH_3)_3Br^-`
B. `CH_3(CH_2)_11N^+(CH_3)_3Br^-`
C. `CH_3(CH_2)_6COO^-Na^+`
D. `CH_3(CH_2)_11OSO3^-Na^+`

Answer

To determine which surfactant forms micelles in aqueous solution at the lowest molar concentration, we need to analyze the given surfactants based on the length of their alkyl chains. The longer the alkyl chain, the lower the concentration required to form micelles.

### Step-by-Step Solution:

1. **Identify the Surfactants**: We have four surfactants (A, B, C, D) to analyze. Each surfactant has a different alkyl chain length.

2. **Determine the Alkyl Chain Lengths**:
- **Surfactant A**: Contains 19 carbon atoms.
- **Surfactant B**: Contains 14 carbon atoms.
- **Surfactant C**: Contains 7 carbon atoms.
- **Surfactant D**: Contains 12 carbon atoms.

3. **Compare the Alkyl Chain Lengths**:
- Surfactant A has the longest alkyl chain with 19 carbon atoms.
- Surfactant B has 14 carbon atoms.
- Surfactant C has 7 carbon atoms.
- Surfactant D has 12 carbon atoms.

4. **Conclusion**: Since surfactant A has the longest alkyl chain, it will form micelles at the lowest molar concentration in an aqueous solution at ambient conditions.

5. **Final Answer**: The surfactant that will form micelles in aqueous solution at the lowest molar concentration at ambient conditions is **A**.