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A solution of an organic compound is pre...

A solution of an organic compound is prepared by dissolving 68.4 g in 1000 g of water.
Calculate the molecular mass of the compound and osmotic pressure of the solution
at 293 K when elevation of b.pt is 0.104 and `K_(b)` for water is `"0.52 K mol"^(-1)`.

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The correct Answer is:
To solve the problem, we will follow these steps: ### Step 1: Calculate the molality of the solution The formula for elevation in boiling point is given by: \[ \Delta T_b = K_b \times m \] Where: - \(\Delta T_b\) = elevation in boiling point - \(K_b\) = ebullioscopic constant - \(m\) = molality of the solution Given: - \(\Delta T_b = 0.104 \, \text{K}\) - \(K_b = 0.52 \, \text{K kg mol}^{-1}\) Rearranging the formula to find molality (\(m\)): \[ m = \frac{\Delta T_b}{K_b} \] Substituting the values: \[ m = \frac{0.104}{0.52} = 0.2 \, \text{mol/kg} \] ### Step 2: Calculate the number of moles of solute Molality is defined as the number of moles of solute per kilogram of solvent. We have 1000 g of water, which is 1 kg. Using the formula: \[ m = \frac{n}{\text{mass of solvent in kg}} \] Where \(n\) is the number of moles of solute. Rearranging gives: \[ n = m \times \text{mass of solvent in kg} \] Substituting the values: \[ n = 0.2 \, \text{mol/kg} \times 1 \, \text{kg} = 0.2 \, \text{mol} \] ### Step 3: Calculate the molecular mass of the compound The molecular mass (M) can be calculated using the formula: \[ M = \frac{\text{mass of solute (g)}}{\text{number of moles (mol)}} \] Given that the mass of the solute is 68.4 g: \[ M = \frac{68.4 \, \text{g}}{0.2 \, \text{mol}} = 342 \, \text{g/mol} \] ### Step 4: Calculate the osmotic pressure of the solution The formula for osmotic pressure (\(\Pi\)) is given by: \[ \Pi = nCRT \] Where: - \(n\) = number of moles of solute - \(C\) = concentration in mol/L (which is equal to \(n/V\), where \(V\) is the volume in liters) - \(R\) = universal gas constant = 0.0821 L·atm/(K·mol) - \(T\) = temperature in Kelvin Since we have 68.4 g of solute in 1000 g of water, we can assume the volume of the solution is approximately 1 L (for dilute solutions). Now, substituting the values: \[ \Pi = nRT = 0.2 \, \text{mol} \times 0.0821 \, \text{L·atm/(K·mol)} \times 293 \, \text{K} \] Calculating: \[ \Pi = 0.2 \times 0.0821 \times 293 \approx 4.83 \, \text{atm} \] ### Final Answers - Molecular mass of the compound = 342 g/mol - Osmotic pressure of the solution = 4.83 atm

To solve the problem, we will follow these steps: ### Step 1: Calculate the molality of the solution The formula for elevation in boiling point is given by: \[ \Delta T_b = K_b \times m \] ...
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