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At 35^@C , the vapour pressure of CS2 is...

At `35^@C` , the vapour pressure of `CS_2` is 512 mm Hg and that of acetone is 344 mm Hg . A solution of `CS_2` in acetone has a total vopour pressure of 600 mm Hg. The false statement amongst the following is

A

A mixture of 100 mL `CS_2` and 100 mL acetone has a volume `lt200 mL`

B

Roult's law is not obeyed by this system

C

Heat must be adsorbed in order to produce the solution at `35^@C`

D

`CS_2` and acetone are less attracted to each other than to themselves

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the given data and apply Raoult's Law to determine which statement is false. ### Step-by-Step Solution: 1. **Understand the Given Data:** - Vapor pressure of pure carbon disulfide (CS₂) at 35°C = 512 mm Hg - Vapor pressure of pure acetone at 35°C = 344 mm Hg - Total vapor pressure of the solution (CS₂ in acetone) = 600 mm Hg 2. **Apply Raoult's Law:** - Raoult's Law states that the total vapor pressure (P_total) of a solution is the sum of the partial vapor pressures of each component: \[ P_{\text{total}} = P^0_A \cdot X_A + P^0_B \cdot X_B \] - Where \(P^0_A\) and \(P^0_B\) are the vapor pressures of the pure components, and \(X_A\) and \(X_B\) are their mole fractions in the solution. 3. **Determine the Maximum Possible Total Vapor Pressure:** - The maximum total vapor pressure occurs when the mole fraction of one component is 1 (i.e., pure component). In this case, the maximum vapor pressure is equal to the vapor pressure of the more volatile component, which is CS₂ (512 mm Hg). - Since the total vapor pressure of the solution (600 mm Hg) is greater than 512 mm Hg, this indicates a positive deviation from Raoult's Law. 4. **Interpret the Positive Deviation:** - A positive deviation means that the interactions between the molecules of different components (CS₂ and acetone) are weaker than the interactions between the molecules of the same component. Therefore, the solution has a higher vapor pressure than predicted by Raoult's Law. 5. **Evaluate the Statements:** - **Statement A:** A mixture of 100 ml carbon disulfide and 100 ml acetone has a volume less than 200 ml. (This is likely false because volumes of miscible liquids typically add up.) - **Statement B:** Raoult's law is not obeyed by this solution. (This is true as we observed a positive deviation.) - **Statement C:** Heat must be absorbed in order to produce the solution at 35°C. (This is true as the solution formation is endothermic due to weaker interactions.) - **Statement D:** CS₂ and acetone are less attracted to each other than to themselves. (This is true as it explains the positive deviation.) 6. **Identify the False Statement:** - The false statement is **Statement A**: A mixture of 100 ml carbon disulfide and 100 ml acetone has a volume less than 200 ml. ### Final Answer: The false statement is **Statement A**.
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