- 22 A Small Test Tube Has A Volume Of 3 Ml 23 A Litmus Paper Test For The Acidity Or Basicity Of A Solution Require 1 (133.84 KiB) Viewed 71 times
22. A "small" test tube has a volume of -3 mL. 23. A litmus paper test for the acidity or basicity of a solution requires the use of a stirring rod to remove a portion of the solution to then be touched to the litmus paper. 24. After drying a hygroscopic solid in a drying oven, the solid should be cooled in a desiccator. The color change of the indicator at the endpoint of a titration should persist for 30 seconds. 25. 16a Answer True or False for the following statements that refer to Laboratory Techniques. Ask your instructor to identify the questions you are to complete. False 1. All clean glassware should be air-dried naturally. True 2. While cleaning glassware, discard all washes and rinses from the delivery point of the glass vessel. True 3. To avoid waste in the use of chemicals, share the unused portion with other chemists before discarding. True 4. Never touch, taste, or smell a chemical unless specifically told to do so. False 5. A chemical with a "blue" hazard label (a number 3 rating) means that the chemical is highly reactive. False 6. If uncertain as to how to dispose of a chemical, dumping it into the sink followed by copious amount of water is a safe disposal procedure. True 7. Use a spatula to transfer solid chemicals from a reagent bottle. false 8. Most all chemicals used in experiments can be discarded into the sink. True 9. The number of significant figures used to record the mass of a chemical should correspond to the sensitiv- ity of the balance used for the measurement. False 10. A 3-inch test tube has a volume of 3 mL; an 8-inch test tube must have a volume of 8 mL. false 11. To transfer a solution, a stirring rod touches the delivery point of the reagent vessel and the wall of the receiving vessel. True 12. The minimum number of centrifuge tubes placed in a centrifuge during its operation is two. True 13. A test tube should be less than one-third full when heating with a "cool" flame. True 14. Right-handed students should operate the stopcock of a buret with their left hand and swirl the Erlenmeyer (receiving) flask with the right hand. 15. The thumb is the digit of choice on controlling the flow of liquid from a pipet. 16. Blow out the solution remaining in the pipet tip after the solution has drained from the pipet. 17. A buret must always be filled to the top (the zero mark) before every titration procedure. 18. The volume of solution in a buret should be read and recorded 10-15 seconds after completing the titration. 19. It is possible to add a half-drop of solution from a buret. 20. To test the acidity of a solution with pH paper, place the pH paper directly in the solution. 21. The odor of a chemical should not be tested unless specifically instructed to do so. The vapors of the chem- ical should be fanned toward the nose. 22. One must first calculate the number of moles of solute that are required before preparing a solution of known concentration. Summarize the Disclaimer in your own words. 42 Laboratory Techniques 17b 15a