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Compare the weigths of methanol and glyc...

Compare the weigths of methanol and glycerol, which would be required separately to lower the freezing point of one Kg water by `10^@`.

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To solve the problem of comparing the weights of methanol and glycerol required to lower the freezing point of 1 kg of water by 10°C, we can follow these steps: ### Step 1: Understand the Concept The freezing point depression (ΔTf) is directly proportional to the molality of the solution and can be expressed as: \[ \Delta T_f = K_f \cdot m \] where \(K_f\) is the freezing point depression constant and \(m\) is the molality of the solution. ### Step 2: Identify the Molecular Weights - The molecular weight of methanol (CH₃OH) is approximately 32 g/mol. - The molecular weight of glycerol (C₃H₈O₃) is approximately 92 g/mol. ### Step 3: Set Up the Relationship Since the freezing point depression is inversely proportional to the molecular weight of the solute, we can set up the following relationship: \[ \frac{\Delta T_f \text{ (methanol)}}{\Delta T_f \text{ (glycerol)}} = \frac{M_{\text{glycerol}}}{M_{\text{methanol}}} \] where \(M\) represents the molecular weight. ### Step 4: Substitute the Values Substituting the known values: \[ \frac{10}{10} = \frac{92}{32} \] This simplifies to: \[ 1 = \frac{92}{32} \] ### Step 5: Calculate the Ratio Now, we can calculate the ratio of the weights required to achieve the same freezing point depression: \[ \frac{W_{\text{methanol}}}{W_{\text{glycerol}}} = \frac{M_{\text{glycerol}}}{M_{\text{methanol}}} = \frac{92}{32} \] This means that for every 92 g of glycerol, we would need 32 g of methanol to achieve the same freezing point depression. ### Step 6: Conclusion Thus, the weight of methanol required is less than that of glycerol to achieve the same lowering of the freezing point of water by 10°C. ### Final Comparison To summarize: - Weight of methanol required: 32 g - Weight of glycerol required: 92 g
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