Question

What is the molecular mass of a molecular compound with a freezing point -.520 degrees C when 6.21 g is dissolved in 500 g of water?

Answer 1

67200 Chemistry, Other

What is the molecular mass of a molecular compound with a freezing point -0.520 degrees C when 6.21 g is dissolved in 500 g of water?

Answer:

$$\begin{array}{l} \Delta T_{fr} = Km \quad m = n / \text{mass} \quad n = m / M \\ K_{\text{water}} = 1.86 \, \text{K} \cdot \text{mol}^{-1} \cdot \text{kg} \\ 0.520 = 1.86 \cdot m \\ m = 0.28 \, \text{mol/kg} \\ n = \text{mass} \cdot m = 0.5 \cdot 0.28 = 0.14 \, \text{mol} \\ M = m / n = 6.21 / 0.14 = 44.36 \, \text{g/mol} \\ \end{array}$$

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