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 solve the question regarding which surfactant will form micelles in aqueous solution at the lowest molar concentration, we need to understand the concept of Critical Micelle Concentration (CMC). Here’s a step-by-step solution:

### Step 1: Understand the Concept of CMC
The Critical Micelle Concentration (CMC) is the concentration of surfactants in a bulk phase above which the surfactants start to form micelles. Micelles are aggregates of surfactant molecules that form in solution when the concentration of surfactants exceeds the CMC.

**Hint:** Remember that surfactants with longer hydrophobic tails generally have lower CMC values.

### Step 2: Analyze the Surfactants
We need to compare the surfactants based on the length of their hydrocarbon chains. The longer the hydrocarbon chain, the lower the CMC, meaning that it will form micelles at a lower concentration.

**Hint:** Look for the surfactant with the longest hydrocarbon chain.

### Step 3: Identify the Surfactants
Assuming we have a list of surfactants with their respective chain lengths:
- Surfactant A: 15 carbon atoms
- Surfactant B: 11 carbon atoms
- Surfactant C: 6 carbon atoms

**Hint:** Write down the number of carbon atoms for each surfactant to compare them easily.

### Step 4: Determine the Longest Chain
From the given surfactants:
- Surfactant A has 15 carbon atoms.
- Surfactant B has 11 carbon atoms.
- Surfactant C has 6 carbon atoms.

Surfactant A has the longest chain.

**Hint:** The surfactant with the longest chain will have the lowest CMC.

### Step 5: Conclusion
Since Surfactant A has the longest hydrocarbon chain (15 carbon atoms), it will form micelles in aqueous solution at the lowest molar concentration. Therefore, the answer to the question is Surfactant A.

**Final Answer:** Surfactant A (with 15 carbon atoms) will form micelles at the lowest molar concentration.