Concentration of a Solution: Mass Percent

Questions and Answers

What is mass percent and how is it calculated?

Mass percent is the mass of solid solute in grams present in 100 grams of the solution, calculated using the formula Mass% = (Mass of solute / Mass of solution) * 100.

How do you determine the volume percent of a solution?

Volume percent is determined using the formula Volume% = (Volume of solute / (Volume of solute + Volume of solvent)) * 100.

Define solubility in the context of a solute's saturation in a solvent.

Solubility is the amount of solute that can dissolve in 100 grams of solvent to form a saturated solution at a specific temperature.

What are the mass solubility of sodium chloride and potassium nitrate in 100 g of water at 40°C?

The solubility of sodium chloride is 36.5 g and the solubility of potassium nitrate is 63 g in 100 g of water at 40°C. Signup and view all the answers

Explain the significance of the mass percent formula in solution concentration.

The mass percent formula helps describe how much solute is present in a solution relative to the total mass, which is crucial for determining concentrations. Signup and view all the answers

What does the term 'saturated solution' mean?

A saturated solution is one where no more solute can dissolve in the solvent at a specific temperature, resulting in undissolved solute present. Signup and view all the answers

Why might mass percent be preferred over volume percent when measuring solutions?

Mass percent is often preferred when the solute is a solid and the solvent is a liquid because it provides a clear measure of the solute's contribution by weight. Signup and view all the answers

What role does temperature play in the solubility of substances?

Temperature affects the solubility of substances; generally, solubility increases with temperature for solids but can vary for gases. Signup and view all the answers

What is a substance with negligible solubility called?

Insoluble. Signup and view all the answers

How does the size of solute particles affect solubility?

Smaller solute particles increase the total surface area, enhancing solubility. Signup and view all the answers

What happens to the solubility of most solids in water as temperature increases?

The solubility usually increases. Signup and view all the answers

Describe what a solubility curve represents.

A solubility curve plots solubility against temperature. Signup and view all the answers

What is unique about the solubility of sodium chloride as temperature increases?

Its solubility increases only slightly with temperature. Signup and view all the answers

What is an example of a salt that first increases and then decreases in solubility with temperature?

Na2SO4.10H2O (Glauber's salt). Signup and view all the answers

How does stirring affect the rate of dissolution?

Stirring increases the contact between solute and solvent, enhancing dissolution. Signup and view all the answers

Which factor decreases the solubility of a gas in a liquid?

An increase in temperature. Signup and view all the answers

What is a key step in determining the solubility of a solute in water?

Weighing a known mass of the solute before mixing. Signup and view all the answers

What occurs when a solute becomes supersaturated?

It can lead to the precipitation of the solute. Signup and view all the answers

Study Notes

Concentration of a Solution

Concentration represents the amount of solute in a specific quantity of solution and can be expressed using various methods.

Mass Percent

Mass percent is calculated using the formula:
> Mass% = (Mass of solute / Mass of solution) * 100
Typically used when solute is a solid and solvent is a liquid.
Example: In a solution with 10 grams of sodium chloride and 90 grams of water, the mass percent is 10%.

Volume Percent

Volume percent is determined using the formula:
> Volume% = (Volume of solute / Total volume of solution) * 100
Most applicable when both solute and solvent are liquids.
Example: Mixing 30 mL of alcohol with 70 mL of water results in a volume percent of 30%.

Solubility

Solubility refers to the amount of solute that can dissolve in 100 g of solvent at a specific temperature.
Different substances have varying solubilities; potassium nitrate has higher solubility compared to sodium chloride in water at 40°C with values of 63 g and 36.5 g, respectively.
A solute's solubility represents the maximum amount needed to saturate a solvent.

Solubility Categories

Insoluble: Substances like silver chloride with negligible solubility (0.000015 g).
Sparingly Soluble: Compounds like calcium hydroxide, which has a solubility of 0.17 g.
Soluble: Highly soluble substances such as sodium chloride.

Factors Affecting Solubility

Size of Solute Particles: Smaller particles increase surface area, enhancing solubility.
Stirring: Promotes greater solvent exposure to solute, accelerating dissolution.
Temperature:
- The solubility of gases in liquids decreases with temperature.
- The solubility of most solids generally increases with temperature (e.g., potassium nitrate solubility rises from 31.6 g at 20°C to 108 g at 60°C).

Variation in Solubility with Temperature

Solubility curves graphically represent solubility changes concerning temperature, with solubility on the y-axis and temperature on the x-axis.

Solubility Curves of Common Compounds

Sodium nitrate and potassium nitrate: exhibit significant increases in solubility with rising temperature.
Sodium chloride: shows slight increases in solubility with temperature.
Hydrated calcium sulfate: solubility initially rises then falls after a certain temperature.

Anomalous Solubility

Certain salts, like Glauber's salt (Na2SO4.10H2O), display increases in solubility up to a specific temperature (32.8°C) before decreasing due to equilibrium with anhydrous forms.

Determining Solubility

Identify the temperature for solubility assessment.
Weigh a specific mass of solute.
Place solute in a known mass of water and agitate.
Heat the solution to the desired temperature.
Calculate dissolved solute mass:
> Mass of solute dissolved = (Total mass of solute - Mass of undissolved solute).

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Description

Learn about the concentration of a solution, including the concept of mass percent, its formula, and examples. Understand how it is used to express the amount of solute in a solution.