Ethanol cannot to concentrated by fractional distillation because :

Options

A. It is an inflammable liquids
B. Its boiling is very close to that of water
C. It forms a constant boiling mixture with water
D. It is soluble in water in all proportions

Answer

To solve the question "Ethanol cannot be concentrated by fractional distillation because:", we will analyze the options provided and understand the concept of fractional distillation and azeotropic mixtures. Here’s a step-by-step solution:

### Step 1: Understand Fractional Distillation
Fractional distillation is a technique used to separate mixtures of liquids based on differences in their boiling points. It is particularly effective when the boiling points of the components differ by less than 25 degrees Celsius.

**Hint:** Fractional distillation is used for separating miscible liquids with close boiling points.

### Step 2: Identify the Components of the Mixture
In this case, we are focusing on ethanol and water. Ethanol has a boiling point of approximately 78.37 °C, while water boils at 100 °C. The boiling points are relatively close, which is a factor in considering fractional distillation.

**Hint:** Check the boiling points of the liquids involved to see if they are close enough for fractional distillation.

### Step 3: Recognize the Azeotropic Behavior
When ethanol is mixed with water in a specific ratio (approximately 95.6% ethanol and 4.4% water by weight), they form an azeotropic mixture. An azeotrope is a mixture that has a constant boiling point and composition throughout the distillation process.

**Hint:** Azeotropes boil at a constant temperature and cannot be separated by simple distillation methods.

### Step 4: Analyze the Azeotropic Mixture
In the case of the ethanol-water mixture, when heated, the vapor produced has the same composition as the liquid mixture. This means that the distillation process will not change the proportions of ethanol and water in the vapor, making it impossible to concentrate ethanol further.

**Hint:** Understand that the vapor produced during boiling retains the same ratio of components as the liquid.

### Step 5: Evaluate the Options
Now, let’s evaluate the options given in the question:
- **A**: It is an inflammable liquid. (Not relevant)
- **B**: Its boiling point is very close to that of water. (Partially true but not the main reason)
- **C**: It forms a constant boiling mixture with water. (Correct)
- **D**: It is soluble in all proportions. (Not relevant)

The correct answer is **C**: Ethanol forms a constant boiling mixture with water, which is the reason it cannot be concentrated by fractional distillation.

**Hint:** Focus on the definition of azeotropic mixtures when evaluating the options.

### Final Answer
Ethanol cannot be concentrated by fractional distillation because it forms a constant boiling mixture (azeotropic mixture) with water.