What is the molality of a solution that has 3 mol of glucose in 6 kg of water?
A. $\frac{3 mol}{6 L}$
B. $\frac{3 kg}{6 L}$
C. $\frac{3 mol}{6 kg}$
D. $\frac{6 kg}{3 mol}$
Answer (1)
Molality is defined as moles of solute per kilogram of solvent.
The solution contains 3 mol of glucose and 6 kg of water.
Calculate molality: 6 kg 3 mol = 0.5 mol/kg .
The molality of the solution is 6 kg 3 mol .
Explanation
Understanding the Problem We are given a solution of glucose in water, and we need to find the molality of the solution. Molality is defined as the number of moles of solute divided by the mass of the solvent in kilograms. In this case, glucose is the solute and water is the solvent.
Applying the Formula We are given that there are 3 moles of glucose and 6 kg of water. We can use the formula for molality to find the molality of the solution:
Molality = Kilograms of solvent Moles of solute
Substituting the Values Now, we substitute the given values into the formula:
Molality = 6 kg 3 mol
Simplifying the Expression We simplify the expression:
Molality = 6 3 kg mol = 0.5 kg mol
Final Answer The molality of the solution is 0.5 mol/kg, which corresponds to option C: 6 kg 3 mol
Examples
Molality is a useful concept in chemistry, especially when dealing with colligative properties such as boiling point elevation and freezing point depression. For example, if you're making antifreeze for your car, you need to know how much ethylene glycol (the solute) to add to water (the solvent) to lower the freezing point to a certain temperature. Calculating the molality helps you determine the correct concentration to achieve the desired freezing point.
