An electric device delivers a current of [tex]$15.0 A$[/tex] for 30 seconds. How many electrons flow through it?
Answer (1)
Solution A is unsaturated because it contains 20g of solute in 100g of water, while the solubility is 37g/100g of water.
Solution B is saturated because it contains 10g of solute in 100g of water, and the solubility is 10g/100g of water.
Solutions C and D are either saturated or supersaturated because they contain more solute than the solubility at 20°C.
Therefore, the unsaturated solution is A: A .
Explanation
Understanding Unsaturated Solutions We need to determine which of the four solutions (A, B, C, and D) is unsaturated. An unsaturated solution is one where more solute can be dissolved in the solvent at a given temperature. We will compare the amount of solute added to the solubility of the solute in each solution at 2 0 ∘ C .
Analyzing Solution A Solution A: 20 g of solute is added to 100 g of water. The solubility of the solute is 37 g / 100 g H 2 O at 2 0 ∘ C . Since 20 g < 37 g, the solution is unsaturated.
Analyzing Solution B Solution B: 10 g of solute is added to 100 g of water. The solubility of the solute is 10 g / 100 g H 2 O at 2 0 ∘ C . Since 10 g = 10 g, the solution is saturated.
Analyzing Solution C Solution C: 65 g of solute is added to 100 g of water and heated. The solubility of the solute is 32 g / 100 g H 2 O at 2 0 ∘ C . Heating the solution increases the solubility. However, since we are determining if the solution is unsaturated at 2 0 ∘ C , and 65 g > 32 g, the solution would be considered saturated or possibly supersaturated if cooled back to 2 0 ∘ C .
Analyzing Solution D Solution D: 7 g of solute is added to 100 g of water and heated. The solubility of the solute is 4 g / 100 g H 2 O at 2 0 ∘ C . Heating the solution increases the solubility. However, since we are determining if the solution is unsaturated at 2 0 ∘ C , and 7 g > 4 g, the solution would be considered saturated or possibly supersaturated if cooled back to 2 0 ∘ C .
Conclusion Based on the analysis, Solution A is the only unsaturated solution because the amount of solute added (20 g) is less than the solubility of the solute at 2 0 ∘ C (37 g / 100 g H 2 O ).
Examples
Understanding solubility is crucial in many real-world applications. For instance, when making coffee, the amount of coffee grounds that can dissolve in hot water determines the strength of the coffee. Similarly, in pharmaceutical formulations, the solubility of a drug affects its absorption and effectiveness in the body. In environmental science, knowing the solubility of pollutants helps predict their movement and impact in water systems. These examples highlight how the principles of solubility are fundamental to various fields.
