Tennessee Wastewater Operator Practice Exam

What substance is added to the distillate when performing the ammonia test to prevent contamination?

1. Nessler's Reagent

2. Sodium Hydroxide

3. Sulfuric Acid

4. Hydrochloric Acid

The correct answer is: Nessler's Reagent

The substance added to the distillate during the ammonia test to prevent contamination is Nessler's Reagent. This reagent is specifically designed for the detection of ammonia in water samples, providing a reliable colorimetric method for measuring ammonia concentrations. Nessler's Reagent contains potassium mercuric iodide, which interacts with ammonia to produce a colored complex. This color change can be quantitatively measured, allowing for accurate determination of ammonia levels in the sample. By using this reagent, any potential contamination of the sample can be minimized, ensuring the integrity of the ammonia test results. The reagent effectively detects ammonia without interference from other substances that may also be present in wastewater. In contrast, sodium hydroxide, sulfuric acid, and hydrochloric acid serve different purposes in various chemical tests and processes. Sodium hydroxide is commonly used to adjust pH levels, while sulfuric acid and hydrochloric acid are strong acids utilized for different types of chemical assays or treatments. These substances do not specifically prevent contamination in the ammonia test context as Nessler's Reagent does.