Practice Problems

Questions on Species (Other than H₂O) Contained in Water

• A small amount (1.0 g) of copper sulfate (CuSO₄), a sky-blue, ionic crystalline solid, is added to 1.0 L of water in a volumetric flask, and vigorously shaken until all of the solid is dissolved.

1. Briefly, describe the major microscopic events that occur in this solvation process. (help)
2. What species (other than H₂O molecules) are present in the resulting solution? (help)

• Tell whether the following mixtures are solutions or suspensions: (help)

1. a clear-looking mixture formed by mixing two ionic solutions
2. a cloudy-looking mixture formed by mixing two different ionic solutions
3. muddy water
4. hydrated Mg²⁺ and Cl^- ions in H₂O

 

Questions on Precipitation

• Explain what happens to the manganese that is added to the water for iron removal. (help)

• Equation 4 shows how Mg²⁺ is removed using lime. However, this process introduces the new water-hardness problem of Ca²⁺ in the water. Propose a way to eliminate this problem. (help)

Questions on the Schematic of a Water-Treatment Plant

• Figure 9, "Filtration in the water-treatment process," shows that adsorption typically occurs before filtration. Briefly, explain why this order of events is important.

• How would the staff at a water-treatment plant know when the filter needs to be cleaned?

(help)

Questions on Point-of-Use Water Treatment

• Eventually, an ion-exchange water-softening device becomes ineffective, because all of the Na⁺ ions have been replaced by Ca²⁺ and Mg²⁺ ions. Briefly, describe a way that you could "refresh" the device (i.e., flush out the Ca²⁺ and Mg²⁺ ions and replenish the Na⁺ ions) using a common kitchen product.

• Can an ion-exchange water-softening device be used to remove organic contaminants?  Briefly explain your answer.

(help)