IIT/JEE Chemistry Practice #7: Molality/Mole Fraction

Dave explains how to solve problems involving molality and mole fraction. He covers three questions: calculating the molality of a salt solution, determining the molality and mole fraction of sugar in syrup, and finding the molality of a sulfuric acid solution. Each problem is broken down step-by-step, emphasizing the importance of understanding the definitions and conversions needed for accurate calculations.

What is the definition of molality?

• Moles of solute per liter of solution

• Moles of solute per kilogram of solvent

• Grams of solute per liter of solution

• Grams of solute per kilogram of solvent

How do you convert grams to moles for a given substance?

• Divide by the molar mass

• Multiply by the molar mass

• Divide by the atomic number

• Multiply by the atomic number

In the first question, what is the molality of the salt solution?

• 0.1 molal

• 0.25 molal

• 0.5 molal

• 0.4 molal

What is the mole fraction of sugar in the syrup solution?

• 0.001

• 0.01

• 0.099

• 0.0999

How do you calculate the mass of solvent in a solution?

• Subtract the mass of solute from the total mass of the solution

• Add the mass of solute to the total mass of the solution

• Multiply the mass of solute by the total mass of the solution

• Divide the mass of solute by the total mass of the solution

What is the molality of the sulfuric acid solution in the third question?

• 9.48 molal

• 11.2 molal

• 10.4 molal

• 12.5 molal

What is the significance of density in calculating molality?

• It is used to convert volume to mass of the solution

• It is used to find the mass of the solute

• It is irrelevant in calculating molality

• It helps in determining the volume of the solution