Concentration Calculations in Solutions

This lesson covers various methods to represent solution concentration, including molarity, percent concentration by mass and volume, and molality. Molarity is useful for stoichiometry but varies with temperature changes. Percent by mass is temperature-independent, while percent by volume is mainly used for liquid solutions. Molality combines the benefits of stoichiometry and temperature independence by relating moles to the mass of the solvent.

Why is molarity not reliable when the temperature changes?

• Because it depends on the volume, which changes with temperature.

• Because it is only used for gases.

• Because it depends on the mass of the solute.

• Because it is not related to stoichiometry.

What does percent concentration represent?

• The ratio of solute to the total solution, without multiplication.

• The ratio of solute to solvent.

• The ratio of solute to the total solution, multiplied by 100.

• The ratio of solvent to the total solution, multiplied by 100.

How is percent by mass calculated?

• Volume of solute divided by volume of solvent, times 100.

• Volume of solute divided by total volume of solution, times 100.

• Mass of solute divided by total mass of solution, times 100.

• Mass of solute divided by mass of solvent, times 100.

In a 3.5% salt solution by mass, how much salt is needed for 100g of solution?

• 3.5g

• 35g

• 0.35g

• 5g

What is the significance of percent by mass being temperature independent?

• It ensures the concentration remains constant regardless of temperature changes.

• It is only applicable to solid solutes.

• It is used for gas solutions.

• It allows for easy conversion to molarity.

What is the main use of percent by volume?

• For solid-liquid solutions.

• For gas-liquid solutions.

• For liquid-liquid solutions.

• For solid-solid solutions.

How is percent by volume different from percent by mass?

• Percent by volume is used for liquid-liquid solutions and can be temperature dependent.

• Percent by volume is used for solid solutions.

• Percent by volume is temperature independent.

• Percent by volume is used for gas solutions.

What is the formula for calculating percent by volume?

• Mass of solute divided by mass of solvent, times 100.

• Volume of solute divided by volume of solvent, times 100.

• Volume of solute divided by total volume of solution, times 100.

• Mass of solute divided by total mass of solution, times 100.

What distinguishes molality from molarity?

• Molality is used for gas solutions.

• Molality is temperature dependent.

• Molality is measured in moles per kilogram of solvent.

• Molality is measured in moles per liter.

Why is molality useful in stoichiometry?

• It is only used for gas solutions.

• It relates moles to volume.

• It is only used for solid solutions.

• It relates moles to mass, which is temperature independent.