A sample of boiler water can be chemically tested for alkalinity by initially adding a few drops of phenolphthalein and then slowly titrating the water sample until the __________.

Correct Answer: Option A — sample color changes from pink to clear

Alkalinity testing using phenolphthalein indicator starts with a magenta-pink color in high pH boiler water. Titrating with standard acid neutralizes the hydroxide and carbonate ions, causing the sample color to transition from pink to clear at the phenolphthalein end point of approximately pH 8.3.