The Blueprint of Water

The Solvent: Problem Set

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⟵ 03 The Solvent (Engineering Notes) · Contents · 03 The Solvent (Answer Key) ⟶

The Solvent: Problem Set

“These are only provided to reinforce understanding. The Engineering Notes contain some of the information that will be required. Make sure to employ dimensional analysis for all unit conversions.”

Level 1: Conceptual Mastery

  1. What is the difference between suspended solids and dissolved solids? Why can’t dissolved solids be removed by conventional filtration?

  2. The chapter describes dissolution as a “transaction.” What are the three energetic terms involved, and which one represents the cost, the payoff, and the wildcard?

  3. Sodium chloride dissolves readily in water while calcium carbonate dissolves reluctantly. Using the language of lattice energy, hydration energy, and entropy, explain why?

  4. Why does conductivity provide a useful estimate of TDS, and what is its most important limitation?

Level 2: Applied Thinking

  1. Your conductivity meter reads 1,450 µS/cm. Estimate the TDS in ppm.

  2. A drum of corrosion inhibitor contains a 3.5% solution of phosphoric acid by mass. Express this concentration in ppm.

  3. You add 5 pounds of NaCl to a 1,000-gallon cooling loop. Assuming complete dissolution, estimate the increase in concentration (ppm).

Level 3: System Integration

  1. A field report lists conductivity as “2.3 mS/cm.” A technician enters it into a spreadsheet as 2.3 µS/cm. By what factor is the TDS estimate wrong, and what operational consequence could this cause?

  2. Two cooling towers both read 2,000 µS/cm conductivity. Tower A’s makeup is high in sodium chloride. Tower B’s makeup is high in calcium bicarbonate. Which tower faces a greater scaling risk, and why does identical conductivity not mean identical behavior?

  3. The chapter explains that groundwater typically has higher TDS than surface water but lower suspended solids. Using the concepts of contact time and filtration through geological formations, explain why this is the case in 2–3 sentences.

Problem notes

Each problem as its own linked note.

3.1 · 3.2 · 3.3 · 3.4 · 3.5 · 3.6 · 3.7 · 3.8 · 3.9 · 3.10

⟵ 03 The Solvent (Engineering Notes) · Contents · 03 The Solvent (Answer Key) ⟶

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