Calculating Molality: Solution Density and Molarity Relationship

• santoki
In summary, molality is a unit of concentration that represents the number of moles of solute per kilogram of solvent and is different from molarity, which represents the number of moles of solute per liter of solution. It is calculated by dividing the moles of solute by the mass of solvent in kilograms. Molality is directly related to solution density and is commonly used for solutions where temperature changes significantly. It affects the boiling and freezing points of solutions through the colligative properties and is more appropriate for solutions where temperature remains constant.
santoki
Question
A 1.392 M sodium carbonate solution has a density of 1.1353 g/mL. Calculate the molality of the solution.

Attempt
1.392 M Na2CO3 = 1.392 mol Na2CO3 per 1 L solution

I can't really make sense out of this. What would be the next step?

What is the definition of molality?

Assume you have 1L of the solution. What is its mass? What is the mass of dissolved sodium carbonate? What is the mass of the solvent?

1. What is molality and how is it different from molarity?

Molality is a unit of concentration that represents the number of moles of solute per kilogram of solvent. It is different from molarity, which represents the number of moles of solute per liter of solution. Molality takes into account changes in temperature and is therefore more accurate for calculating concentration in solutions where temperature changes significantly.

2. How do you calculate molality?

Molality (m) can be calculated by dividing the moles of solute (n) by the mass of solvent (m) in kilograms. The formula is: m = n / m.

3. How is solution density related to molality?

Solution density is directly related to molality, as it is the mass of the solute per unit volume of the solution. As the molality increases, the density of the solution also increases, assuming all other factors remain constant.

4. Can molality be used to calculate concentration for all types of solutions?

Molality is generally used for solutions where temperature changes significantly, such as in chemical reactions. It is not as commonly used for dilute solutions or solutions where temperature remains constant. In these cases, molarity is a more appropriate unit of concentration.

5. How does molality affect the boiling and freezing points of solutions?

Molality affects the boiling and freezing points of solutions through the colligative properties of solutions. As the molality increases, the boiling point of the solution increases and the freezing point decreases. This is due to the interactions between the solute particles and the solvent, which disrupt the normal boiling and freezing processes.

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