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Praxis Middle School: Science (5442)
Questions and Answers Latest Version with Certified Solutions
What is the purpose of a calibration curve in spectrophotometry?✔✔To determine the concentration of an unknown sample by comparing its absorbance to a standard series
Why is a blank solution used in colorimetric analysis?✔✔To zero the instrument and eliminate background absorbance from solvents or reagents
What does a higher absorbance value typically indicate about a solution in UV-Vis spectroscopy?✔✔That the solution has a higher concentration of the absorbing substance
Why is it important to use distilled water in analytical procedures?✔✔To avoid contamination that could interfere with results
What is the function of an indicator in a titration? 1 / 3
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✔✔To signal the endpoint of the reaction by changing color
Why are burettes preferred over graduated cylinders in titration experiments?✔✔Because burettes allow precise delivery of liquid volumes
What type of substance is commonly used as a primary standard in titrations?✔✔A highly pure, stable compound with a known concentration
What information can be gained from a titration curve?✔✔The equivalence point and pH changes during a titration
Why must glassware be rinsed with the solution it will contain during a titration?✔✔To prevent dilution and ensure accurate measurements
What is gravimetric analysis used for?✔✔To determine the amount of an analyte by measuring mass
Why is it important to dry a precipitate before weighing in gravimetric analysis? 2 / 3
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✔✔To remove moisture that could affect mass accuracy
What is the role of a reagent in qualitative analysis?✔✔To cause a specific reaction that identifies the presence of a substance
Why is it necessary to use a control sample in analytical experiments?✔✔To provide a baseline for comparison and detect experimental errors
What is the difference between accuracy and precision in analytical chemistry?✔✔Accuracy refers to how close a measurement is to the true value, while precision refers to the consistency of repeated measurements
What is the function of a buffer solution in chemical analysis?✔✔To maintain a stable pH during a reaction
Why should samples be handled with gloves and clean tools during analysis?✔✔To prevent contamination and ensure valid results
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