CWEA GRADE I LABORATORY ANALYST QUESTIONS WITH CORRECT ANSWERS

Chloride CORRECT ANSWER - Major anion found in many natural waters - Can impart salty taste in H2O What increases concentration of chloride in wastewater CORRECT ANSWER Chloride in human diet and softeners flushed into sanitary sewer system 2 most prevalent methods of measuring chloride CORRECT ANSWER argentometric and mercuric nitrate Argentometric CORRECT ANSWER Titration of sample with standard solution of silver nitrate (AgNO3) - Indicator: Chromate ions (CrO4) - End point: reddish silver chromate Mercuric Nitrate CORRECT ANSWER Titration with standard mercuric nitrate solution -pH must be adjusted between 2.3 and 2.8 - Indicator: Diphenyl carbazone - End point: Change from blue to purple in presence of mercury Interference of Mercuric Nitrate Method CORRECT ANSWER Sulfide, bromide, orthophosphate (over 30 ppm), and iodide Why does color change in water CORRECT ANSWER Presence of decaying vegetable matter, metal ions (ie. iron) or industrial and domestic pollution How is color measured CORRECT ANSWER Measured using visual comparison method Visual comparison method CORRECT ANSWER Sample compared to standards using matched Nessler tubes - Standards prepared with solution containing cholorplatinate and cobaltous chloride Standard units for color CORRECT ANSWER One unit= color resulting from 1 mg of platinum/L 2 color reporting CORRECT ANSWER True and Apparent True color CORRECT ANSWER Color from dissolved substances, determine using sample treated to remove turbidity Apparent Color CORRECT ANSWER Includes dissolved