Question

summarize it

1. if a student wants to decrease the concentration of an aqueous solution, what should be done?

a. the student should add more solvent to the solution.
b. the student should add more solute to the solution.
c. the student should agitate the solution.
d. the student should decrease the surface area of the solution.

1. what is the effect of agitating a solution of protein powder and drinking water?

a. stirring decreases the density of the protein powder, making it float.
b. agitation decreases the surface area of the solute.
c. agitation helps decrease the concentration of the solution.
d. stirring the solution helps increase the rate of dissolution.

1. a student in a laboratory wants to increase the concentration of salt in salt water. what is one

correct way to achieve this effect?
a. freeze the solution, which increases the volume of the solution.
b. agitate the solution.
c. heat the solution, causing some of the solvent to evaporate.
d. add more water to the solution to dilute it.

1. identify the solute and the solvent in the following aqueous solutions.

Explanation:

1. Concentration of a solution is calculated as \( \frac{\text{amount of solute}}{\text{amount of solution}} \). To decrease the concentration, we can increase the amount of solvent (since \( \text{solution}=\text{solute}+\text{solvent} \)). Agitating the solution affects the rate of dissolution, not the concentration. Decreasing the surface - area of the solution has no direct relation to concentration. Adding more solute would increase the concentration.
2. Agitating (stirring) a solution helps to increase the rate of dissolution. It does not change the density of the solute (protein powder in this case) in a way that makes it float. Agitation does not decrease the surface area of the solute; rather, it can help in distributing the solute better. Agitation affects the rate of dissolution, not the concentration of the solution (concentration is about the ratio of solute to solution).
3. To increase the concentration of salt in salt - water (\( \text{concentration}=\frac{\text{salt}}{\text{salt + water}} \)), we can decrease the amount of solvent (water). Freezing the solution increases the volume (due to the expansion of water on freezing) which would decrease the concentration. Agitating the solution affects the rate of dissolution. Adding more water (solvent) would decrease the concentration. Heating the solution and evaporating some solvent (water) would increase the concentration as the amount of solute (salt) remains the same while the amount of solution (salt + water) decreases.
4. In an aqueous solution, water is usually the solvent.

• For orange juice: The solute is the juice extract (contains sugars, flavor compounds, etc.) and the solvent is water.
• For tea: The solute is the tea extract (contains tannins, flavor compounds) and the solvent is water.
• For pool water: The solute could be chemicals like chlorine, salts (if any added for maintenance) and the solvent is water.
• For vinegar (acetic acid): The solute is acetic acid and the solvent is water.

Answer:

1. A. The student should add more solvent to the solution.
2. D. Stirring the solution helps increase the rate of dissolution.
3. C. Heat the solution, causing some of the solvent to evaporate.

4.

Solution	Solute	Solvent
Tea	Tea extract (tannins, flavor compounds)	Water
Pool water	Chlorine, salts (if added)	Water
Vinegar (acetic acid)	Acetic acid	Water