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The MicroLab Interface: Plotting Measured Data to Generate a Graph

Outline. PurposeAcid-Base ReactionspH and IC probe functionWaste and SolutionsWhat to turn inNext Assignment. Purpose. You will learn to use MicroLab for data acquisition and analysis.A graphical representation of temperature and pH changes will demonstrate chemical changes related to acid-ba

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The MicroLab Interface: Plotting Measured Data to Generate a Graph

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    1. The MicroLab Interface: Plotting Measured Data to Generate a Graph Experiment 3

    2. Outline Purpose Acid-Base Reactions pH and IC probe function Waste and Solutions What to turn in Next Assignment

    3. Purpose You will learn to use MicroLab for data acquisition and analysis. A graphical representation of temperature and pH changes will demonstrate chemical changes related to acid-base reactions.

    4. pH The pH scale ranges from 0 to 14. The pH of a solution tells us if that solution is acidic, basic or neutral.

    5. Acids Acids are compounds that donate H+ to a solution. The pH of an acid always falls below 7. The stronger the acid, the closer the pH is to 0. HCl (hydrochloric acid) and HNO3 (nitric acid) are considered strong acids.

    6. Bases Bases are compounds that donate OH- to solutions. The pH of bases always fall above 7. The stronger the base, the closer the pH is to 14. NaOH (sodium hydroxide) and KOH (potassium hydroxide) are considered strong bases.

    7. Neutral Solutions Neutral Solutions have a pH of about 7. These solutions are neither acidic nor basic. Water is considered neutral.

    8. Acid-Base Reactions HCl(aq) + NaOH(aq) ? H2O(l) + Na+(aq) + Cl-(aq) + heat A strong acid and a strong base react to produce water and a salt (neutralization). This process releases heat (exothermic reaction). We can measure the change in temperature that takes place. We can measure the pH change.

    9. Calculations You can determine the volume of base needed to complete your reaction today by using the equation MaVa = MbVb You must know the values for the other three variables first.

    10. Calculations Ma = 0.25* M HCl Va = 85.0 mL Mb = 0.25* M NaOH Vb = Unknown Vb = *Get the exact number from the appropriate carboy!

    11. pH and Temperature Probes Be careful! These probes are fragile. You will use a pre-calibrated template for both the temperature and pH probes. Remember to rinse and dry the probes before each transfer. This will prevent cross-contamination. Your instructor will show you how to set up your probes and glassware.

    12. Safety Concerns Reagents: HCl (< 10%) / HNO3 (5 20%) NaOH / KOH Eye Contact: Irritation, tearing, redness, pain, severe burns, impaired vision, permanent eye damage, and blindness Skin Contact: Irritation, corrosion, redness, pain, and severe skin burns. Inhalation: Corrosion, coughing, choking, inflammation of the nose, throat, and upper respiratory tract, severe burns, pulmonary edema, circulatory failure, and death. Ingestion: Nausea, vomiting, diarrhea, abdominal pain, mucous membrane corrosion, perforation of the stomach and esophagus, pain and burns to the mouth, throat, esophagus and gastrointestinal tract, and death.

    13. Waste and Solutions Conserve distilled water during cleanup! Dispose of waste in the appropriate waste receptacles. Basic solutions / waste need to be disposed in the base waste container in the fume hood. Acidic solutions / waste need to be disposed in the acid waste container in the fume hood. Solutions with a pH between 6 and 8 can be disposed down the drain. .

    14. What to turn in Make sure all your questions are answered. Turn in a completed report, including: Two graphs Complete and submit your post-lab questions by the deadline.

    15. Next Assignment Experiment 4 Read the required reading sections in your textbook and lab manual. Complete and submit your pre-lab questions by the deadline. Go through the significant figure Molar Mass calculation tutorial in Blackboard before attempting these questions. Use the Periodic Table in your lab manual! If your class is required to complete quizzes in Blackboard, remember to do so.

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