Molality Calculation: How Much NaCl is Needed for a 0.35 Molal Solution?

In summary, molality is a measure of the concentration of a solute in a solvent, expressed in moles of solute per kilogram of solvent. It differs from molarity in that it is based on the mass of the solvent rather than the volume of the solution, making it more accurate for solutions that experience changes in volume. To calculate molality, divide the number of moles of solute by the mass of the solvent in kilograms. Molality is also different from mole fraction, which is a measure of the proportion of a particular component in a mixture of substances. Molality is commonly used in chemistry and biochemistry, as well as in the food and beverage industry, to determine the concentration of solutes in solutions.
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Homework Statement


How many grams of NaCl must you add to 750g of water to make a 0.35 molal solution?

Ans. 7.59g

Homework Equations


[tex]molality=\frac{mol_{solute}}{kg_{solvent}}[/tex]
MW of NaCl = 23 + 35.45 = 58.45 g/mole

The Attempt at a Solution


[tex]0.35mol/kg=\frac{mass(\frac{1mole}{58.45g})}{0.750kg}[/tex]
[tex]mass = 15.33g[/tex]
 
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1. What is molality?

Molality is a measure of the concentration of a solute in a solvent, expressed in moles of solute per kilogram of solvent.

2. How is molality different from molarity?

Molality is based on the mass of the solvent, while molarity is based on the volume of the solution. This means that molality is a more accurate measure of concentration for solutions that experience significant changes in volume due to temperature or pressure.

3. How do you calculate molality?

To calculate molality, divide the number of moles of solute by the mass of the solvent in kilograms.

4. What is the difference between molality and mole fraction?

Molality is a measure of the concentration of a solute in a solvent, while mole fraction is a measure of the proportion of a particular component in a mixture of substances. Molality is expressed as moles of solute per kilogram of solvent, while mole fraction is a ratio of moles of one component to the total moles in the solution.

5. How is molality used in real-world applications?

Molality is commonly used in chemistry and biochemistry, particularly in experiments or processes that involve changes in temperature or pressure. It is also used in the food and beverage industry to determine the concentration of solutes in solutions such as sugar in a drink or salt in a brine solution.

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