The Blueprint of Water

The Power of Hydrogen: Problem Set

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⟵ 04 The Power of Hydrogen (Engineering Notes) · Contents · 04 The Power of Hydrogen (Answer Key) ⟶

The Power of Hydrogen: 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 self-ionization? Why does pure water contain both H⁺ and OH⁻, even though no acid or base has been added?

  2. The chapter says “We are measuring one side of a linked equilibrium.” Explain what this means in your own words.

  3. Pure water at 100°C has a pH of approximately 6.14. Is it acidic? Why or why not?

  4. The chapter distinguishes pH from alkalinity: “pH describes the current intensity of equilibrium. Alkalinity describes the future capacity to resist change.” Why is this distinction important?

Level 2 - Applied Thinking

  1. What is the concentration of [H⁺] and [OH⁻] at pH 4? At pH 10? Show how pH + pOH = 14 holds for each.

  2. How many times more hydrogen ions are present at pH 4 than at pH 7?

  3. A sample has pH 9 at 25°C. Calculate (a) the pOH, (b) [OH⁻], and (c) [H⁺].

Level 3 - System Integration

  1. During an acid cleaning, your solution sits at pH 2.5. You add caustic and the pH moves to 3.5. By what factor did the hydrogen concentration decrease? Explain why a technician might mistakenly think this change was trivial.

  2. You must neutralize 1,000 gallons of acid cleaning solution from pH 1.0 to pH 7.0 using 100% KOH (56.1 g/mol). How many pounds of KOH are required? If the starting pH had been 2.0 instead, how many pounds would be needed?

(Assume an ideal strong-acid solution with no buffering, no dissolved carbonate reserve, and no volume change.)

  1. The chapter describes pH as reorganizing the “rules of chemistry” rather than simply adjusting a dial. Name two specific consequences of a pH shift mentioned in the chapter and explain why even a small change matters.

Problem notes

Each problem as its own linked note.

4.1 · 4.2 · 4.3 · 4.4 · 4.5 · 4.6 · 4.7 · 4.8 · 4.9 · 4.10

⟵ 04 The Power of Hydrogen (Engineering Notes) · Contents · 04 The Power of Hydrogen (Answer Key) ⟶

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