What volume of ethylene glycol $\left(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}_{2}\right),$ a nonelectrolyte,must be added to 15.0 \(\mathrm{L}\) water to produce an antifreeze solution with a freezing point of \(-25.0^{\circ} \mathrm{C} ?\) What is the boiling point of this solution? (The density of ethylene glycol is \(1.11 \mathrm{g} / \mathrm{cm}^{3},\) and the density of water is 1.00 \(\mathrm{g} / \mathrm{cm}^{3} . )\)

Short Answer

Expert verified
To find the volume of ethylene glycol needed to produce an antifreeze solution with a freezing point of -25.0°C, we need to first find the molality, then convert it to moles and finally to volume. The molality is calculated as: \(m = \frac{25.0}{1.86}\). This gives us the moles of ethylene glycol needed: \(Moles_{ethylene\ glycol} = \frac{25.0}{1.86} \times \frac{15000}{1000} \). Then, we can find the mass of ethylene glycol and its volume: \(Volume_{ethylene\ glycol} = \frac{Mass_{ethylene\ glycol}}{Density_{ethylene\ glycol}}\). To find the boiling point of this solution, we can use the boiling point elevation formula: \(\Delta T_b = 1 \cdot 0.512 \cdot \frac{25.0}{1.86}\). The final boiling point would be the sum of the boiling point elevation and the normal boiling point of water (100°C): \(Boiling\ point_{solution} = 100 + \Delta T_b\).

Step by step solution

01

Find the molality needed to reach the desired freezing point

First, we'll determine the molality (moles of solute per kilogram of solvent) needed for the solution to have a freezing point of -25.0°C. Freezing point depression can be calculated using the formula: \(-\Delta T_f = i \cdot K_f \cdot m\) Where \(\Delta T_f\) represents the change in freezing point (in this case, 25.0°C, since the normal freezing point of water is 0°C), \(i\) is the van't Hoff factor (number of particles into which a solute dissociates; since ethylene glycol is a nonelectrolyte, its van't Hoff factor is 1), \(K_f\) is the molal freezing-point depression constant for water (1.86 °C·kg/mol), and \(m\) is the molality. To find the molality, we can rearrange the formula and solve: \(m = \frac{-\Delta T_f}{i \cdot K_f} = \frac{25.0}{1 \cdot 1.86}\)
02

Calculate the moles of ethylene glycol

Now that we have the molality, we can find the number of moles of ethylene glycol needed. We know that there are 15.0 L of water in the solution, which has a density of 1.00 g/cm³. First, we need to convert the volume of water into mass: \(Mass_{water} = 15.0 \ \mathrm{L} \times 1000 \ \mathrm{cm}^{3}/\mathrm{L} \times 1.00 \ \mathrm{g}/\mathrm{cm}^{3} = 15000 \ g\) Now we can use the molality to calculate the moles of ethylene glycol: \(Moles_{ethylene\ glycol} = molality \times Mass_{solvent} = \frac{25.0}{1.86} \times \frac{15000}{1000} \)
03

Convert moles of ethylene glycol to volume

Now, we'll convert the moles of ethylene glycol into volume. First, we need to determine the gram-molecular mass of ethylene glycol: Molar mass of ethylene glycol = (2 × 12.01) + (6 × 1.01) + (2 × 16.00) = 62.08 g/mol We can now find the mass of ethylene glycol needed: \(Mass_{ethylene\ glycol} = Moles_{ethylene\ glycol} \times Molar\ mass_{ethylene\ glycol}\) And finally, we can determine the volume of ethylene glycol using its given density: \(Volume_{ethylene\ glycol} = \frac{Mass_{ethylene\ glycol}}{Density_{ethylene\ glycol}}\)
04

Determine the boiling point of the solution

Now that we've found the volume of ethylene glycol needed, we can determine the boiling point of this solution using the boiling point elevation formula: \(\Delta T_b = i \cdot K_b \cdot m \) Where \(K_b\) is the molal boiling-point elevation constant for water (0.512 °C·kg/mol). Since we've already calculated the molality in Step 1, we can directly plug it into the formula: \(\Delta T_b = 1 \cdot 0.512 \cdot \frac{25.0}{1.86}\) The final boiling point would be the sum of the boiling point elevation and the normal boiling point of water (100°C): \(Boiling\ point_{solution} = 100 + \Delta T_b\)

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