🔍 Key Concepts

• Boiler water chemistry and why certain properties must be controlled to prevent scale and corrosion • The typical use of phenolphthalein in chemistry (what pH range it changes color in) • Which boiler water test specifically relies on an indicator that responds to pH (acidity/alkalinity) rather than to specific ions like chloride or hardness minerals

💭 Think About

• Think about what phenolphthalein actually does in a chemistry lab. When do you usually see it used, and what kind of titration is it involved in? • Which of the listed properties (chloride content, hydrazine, hardness, alkalinity) would most logically be checked using a color-change that occurs at a certain pH? • Eliminate any answer choices that are normally measured with special reagents, test kits, or instruments designed for that specific substance rather than a simple acid-base indicator.

✅ Before You Answer

• Recall that phenolphthalein changes color in a specific pH range (around slightly basic conditions). Match that to the option most directly related to pH. • Verify which properties like chlorides and hardness are usually measured by comparing drops of reagents or titrations with different indicators, not necessarily phenolphthalein. • Confirm in your engineering/boiler chemistry notes which boiler water test is commonly called the "P" test and what it measures.