At what acid/alkalinity ratio does failure occur and pH drop?

• A. 0.25
• B. 0.80
• C. 0.10
• D. 0.40

Answer: (B)

When you think about acid and alkalinity, the key idea is buffering: alkalinity neutralizes acids and keeps the pH from dropping. As acid loading increases, the acid/alkalinity ratio rises, and buffering gets overwhelmed. When that ratio reaches about 0.8, there’s very little buffering left, so a small additional acid causes a noticeable pH drop and potential process failure.

That’s why the 0.80 value is the best answer: it marks the point at which buffering capacity tends to be exhausted and pH falls. The smaller ratios indicate more buffering remains, so they’re less likely to cause immediate pH collapse.