The vapour pressure of pure benzene at a certain temperature is 640 mm Hg. A nonvolatile nonelctrolyte solid weighing `2.175g` is added to `39g` of benzene. The vapour pressure of the solution is `600mmHg`. What is the molecular weight of the solid substance ?

Explanation

To find the molecular weight of the non-volatile non-electrolyte solid, we can use Raoult's law and the concept of colligative properties. Here’s a step-by-step solution:

### Step 1: Understand the problem
We have the vapor pressure of pure benzene (P₀) and the vapor pressure of the solution (P). We need to find the molecular weight (M) of the solid that was added to the benzene.

### Step 2: Use Raoult's Law
According to Raoult's law, the change in vapor pressure (ΔP) can be expressed as:
\[ \Delta P = P₀ - P \]
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