Percentage Composition: The concentration of solutions can be expressed in percentage composition through four
different ways: percentage weight/weight, percentage weight/volume, percentage volume/weight, and percentage
volume/volume.
Interconversion of Concentration Units: Solutions with different concentration units can be converted into each
other, such as converting molarity to molality or weight/weight percentage. This conversion is essential for
laboratory work and requires knowledge of formula masses and densities of solutes or solutions.
What are the four different ways to express percentage composition of solutions?
Answer:
1-Percentage weight/weight
2-Percentage weight/volume
3-Percentage volume/weight
4-Percentage volume/volume
When do we need to convert one unit of concentration into another?
We need to convert concentration units when we have a prepared solution with a known concentration unit but need to know its concentration in another unit.
What is the indirect expression of the ratio of moles of solute to moles of solvent in a solution?
Molality of a solution is the indirect expression of the ratio of moles of the solute to the moles of the solvent.
How does the value of concentration in molality change with temperature compared to molarity?
The value of concentration given in molality does not change with temperature, unlike molarity which is affected by temperature due to volume changes in liquids.
What is the mole fraction of a component in a mixture defined as?
The mole fraction of a component in a mixture is the ratio of the number of moles of that component to the total number of moles of all components present.
What does molality measure in a solution?
a) Moles of solute per liter of solution
b) Moles of solute per kilogram of solvent
c) Volume of solute per volume of solution
d) Mass of solute per volume of solution
Answer: b) Moles of solute per kilogram of solvent
Which of the following is a percentage composition unit for solutions?
a) Molarity
b) Molality
c) Percentage weight/volume
d) Mole fraction
Answer: c) Percentage weight/volume
What is the mole fraction of a component in a mixture?
a) Ratio of moles of solute to moles of solvent
b) Ratio of moles of solute to total moles of all components
c) Ratio of volume of solute to volume of solvent
d) Ratio of mass of solute to mass of solvent
Answer: b) Ratio of moles of solute to total moles of all components
Which concentration unit is independent of temperature changes?
a) Molarity
b) Molality
c) Mole fraction
d) Percentage composition
Answer: b) Molality
What does a 0.2 molal solution indicate?
a) 0.2 moles of solute per liter of solution
b) 0.2 moles of solute per kilogram of solvent
c) 0.2 moles of solute per kilogram of solution
d) 0.2 moles of solute per liter of solvent
Answer: b) 0.2 moles of solute per kilogram of solvent