Solution Concentration Quiz

What does molality (m) specifically measure in a solution?

In the context of solution concentration, which measurement is temperature-independent?

How is the mole fraction (X) of a solute calculated?

What is the formula for parts by mass (m/m)?

What is the molality of a solution containing 80.9 g of HBr dissolved in 1.00 kg of H₂O?

What would the mass fraction of HBr be in a solution where 80.9 g of HBr is in 1080.9 g of solution?

Which statement is true regarding different concentration measures like molality and parts by mass?

If a solution has a mass fraction of 0.0025, what would its concentration in parts per million (ppm) be?

Solution Concentration

Molarity (M) is moles of solute per liter of solution.
Molarity is not ideal for precise measurements because volume changes with temperature.
Molality (m) is moles of solute per kilogram of solvent.
Molality is temperature-independent.
Mole fraction (X) is a direct measure of the number of molecules of a compound present.
It's calculated by dividing the moles of a component by the total moles of all components in the solution.
Parts by mass (m/m) is a quick way to compare different concentrations.
It's calculated by dividing the mass of solute by the total mass of the solution.
Parts by mass and mole fraction are different.
Mole fraction is weighted by the number of molecules.
Parts by mass is weighted by the mass of molecules.

Example Calculation

Calculate molality, mole fraction, and mass fraction of a solution containing 80.9 g of HBr and 1.00 kg of H₂O.
Molality: 1.00 mol HBr / 1.00 kg H₂O = 1.00 molal
Mole fraction of HBr: 1.00 mol HBr / (1.00 mol HBr + 55.5 mol H₂O) = 0.0177
Mass fraction of HBr: 80.9 g HBr / (80.9 g HBr + 1000 g H₂O) = 0.0749
Percent mass: 7.49% or 74.900 ppm
Different molal solutions of HF, HCl, or HBr in water will have the same mole fraction.
However, their parts by mass will be different.

Test your understanding of solution concentration concepts, including molarity, molality, mole fraction, and parts by mass. This quiz features example calculations and helps reinforce the differences between these measures. Perfect for students in chemistry classes.