Why can dilute solutions of hydrogen peroxide not be concentrated by heating? How can a conentrated solution of hydrogen peroxide be obtanied ?

Explanation

### Step-by-Step Solution

**Step 1: Understanding the Decomposition of Hydrogen Peroxide**
- Dilute solutions of hydrogen peroxide (H2O2) cannot be concentrated by heating because they decompose before reaching their boiling point.
- The decomposition reaction of hydrogen peroxide can be represented as:
\[ 2 H_2O_2 \rightarrow 2 H_2O + O_2 \]
- This reaction occurs at temperatures lower than the boiling point of water, which means that heating the solution will lead to the breakdown of H2O2 rather than concentrating it.

**Step 2: Obtaining Concentrated Hydrogen Peroxide**
- To obtain a concentrated solution of hydrogen peroxide from a dilute solution, a series of steps can be followed:

**Step 2.1: Slow Evaporation**
- Start with slow evaporation of the dilute H2O2 solution on a water bath.
- This process will concentrate the solution to approximately 50% H2O2.

**Step 2.2: Dehydration**
- Next, perform dehydration using concentrated sulfuric acid (H2SO4) in a vacuum desiccator.
- This step will further concentrate the solution to about 90% H2O2.

**Step 2.3: Distillation Under Reduced Pressure**
- The third step involves distillation of the solution under reduced pressure.
- By doing this at temperatures between 303 K to 313 K, the water (H2O) will boil off, allowing you to obtain a solution that is approximately 99% H2O2.

**Step 2.4: Removal of Final Traces of Water**
- Finally, to achieve a 100% concentrated solution of hydrogen peroxide, remove any remaining traces of water by freezing the solution using dry ice.
- This step ensures that all water is eliminated, resulting in a pure concentrated solution of H2O2.

### Final Result
- By following these steps, you can successfully obtain a concentrated solution of hydrogen peroxide.