Isotonic solutions must have the same………..

Options

A. solute
B. density
C. elevation in boiling point
D. depression in freezing point

Explanation

To solve the question "Isotonic solutions must have the same...", we need to understand the concept of isotonic solutions and their properties. Here’s a step-by-step breakdown of the solution:

### Step 1: Define Isotonic Solutions
Isotonic solutions are solutions that have the same osmotic pressure. This means that when two solutions are separated by a semipermeable membrane, there will be no net movement of solvent molecules between them.

**Hint:** Remember that isotonic solutions are about balance in osmotic pressure.

### Step 2: Identify Key Properties
Isotonic solutions also have the same concentration of solute particles. This is crucial because the osmotic pressure of a solution is directly related to the concentration of solute particles present in it.

**Hint:** Concentration is a key factor in determining osmotic pressure.

### Step 3: Consider Colligative Properties
Colligative properties, such as boiling point elevation and freezing point depression, depend on the number of solute particles in a solution rather than the identity of the solute. Since isotonic solutions have the same concentration, they will also exhibit the same colligative properties.

**Hint:** Colligative properties are influenced by the quantity of solute, not its type.

### Step 4: Analyze the Options
Given the options—solute, density, elevation in boiling point, and depression in freezing point—only the last two relate to colligative properties. Since isotonic solutions have the same concentration, they will have the same elevation in boiling point and the same depression in freezing point.

**Hint:** Focus on colligative properties when considering isotonic solutions.

### Step 5: Conclusion
Thus, the correct answer is that isotonic solutions must have the same elevation in boiling point and depression in freezing point.

**Final Answer:** Isotonic solutions must have the same elevation in boiling point and depression in freezing point.