1AL F23 Exp 11 Acids C Report Sheet

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University of California, Berkeley *

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1AL

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Chemistry

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Dec 6, 2023

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pdf

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Report sheets must be submitted in the correct order or they will not be graded! Submit one pdf to gradescope with the report sheet pages in order and your notebook pages at the end. Report Sheet Name Partner(s) Your titration data: Table 1: Titration data for your assigned titrant. ] For 1st equivalence point For 2nd equivalence point Solution . . 1 1 (M and identity) Initial pH pI:I at Vo!ume at pH at pI:I ats Vo!ume at pH at Final pH equivalence equivalence equivalence | equivalence equivalence equivalence 1. Generate a titration curve for your sample, a graph of pH vs. Volume Titrant. Label all the data points and regions on the titration curve listed in the data table. Either draw the titration curve on the graph provided below or use a program like Excel to generate the titration curve (See Appendix on Excel). If using Excel, paste a picture of your curve below over the graph paper provided. Remember not to change the template of the report sheet or page layout! 235

2. Based on your assigned solution and its concentration, calculate the predicted volume (in mL) needed to reach the first equivalence point. 3. Does your titration curve data match the predicted volume at equivalence? 4. Explain possible causes of differences or errors in your data. Results and Discussion: Data from all the acids and bases titrated by the ISF staff are shown below. The ISF staff are experts at titration! Nitric Acid (HNO,) Phosphoric Acid (H,PO,) 14.00 1200 ez 10.00 :' - 8.00 f 2 6.00 ; 4.00 3 2.00 E====TTeeeememmmnT 0.00 0.00 2.00 4.00 6.00 800 10.00 12.00 0.00 2.00 4.00 6.00 800 10.00 12.00 mL 0.1000M NaOH mL 0.1000M NaOH ——0.010M -----0.020M ——0.010M =-----0.020M Sulfuric Acid (H,S0,) Sodium Carbonate (Na,CO,) 14.00 12.00 10.00 - 8.00 2 6.00 4.00 2.00 0.00 0.00 2.00 4.00 6.00 800 10.00 12.00 0.00 2.00 4.00 6.00 800 10.00 12.00 mL 0.1000M NaOH mL 0.1000M Hcl ——0.010M -----0.020M ——0.010M =-----0.020M 5. What is the definition of a strong acid? A weak acid? 236

6. Which of the acids studied are weak? Which are strong? How can you tell from the data? 7. Calculate the pKa for the weak acids from the Ka values given in the lab manual. 8. Examine the data from the ISF for the two nitric acid (HNQO3) titrations. What is the volume at equivalence for each? Does this match predictions based on concentration? Explain. Acid Rain and Buffers In the Midwest, the natural geologic formations are typically made of limestone (CaCO3). The limestone in the Midwest provides the lakes and soils with a natural buffer. The questions below highlight the benefits of natural buffers, or buffers in general. Pure Water 9. What is the pH of 1.000 L of pure water? 10. If you add strong acid to pure, unbuffered water, what magnitude of pH change do you expect? (pH drops a little, a lot, not at all) 11. A 200.00 mL sample of 1.000 M nitric acid was added to the water sample above. What is the resulting pH? 237

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Carbonate Buffer 12. What is the pH of a carbonate buffer solution prepared by mixing 1.500 mol of Na2CO3 and 1.000 mol of NaHCO3 and adding water to make a 1.000 L solution? (pKa of HCO3™ is 10.32) 13. If you add strong acid to buffered water, what magnitude of pH change do you expect? (pH drops a little, a lot, not at all) 14. A 200.00 mL sample of 1.000 M nitric acid was added to the buffered solution above. What is the resulting pH? 15. Explain conceptually the process by which limestone (CaCO3) can protect the lakes in the Midwest from the effects of acid rain. (Hint: CaCOs + acid = ??7?) How can real-time analysis be used to reduce pollution? Last week you explored the strengths and limitations of indicator titrations for measuring the acidity of ocean water and determining if a lake or stream is affected by acid rain. 16. Could potentiometric titrations determine if a lake or stream is affected by acid rain? For example, would this technique allow you to say if the lake or stream was acidified from local industrial facility runoff versus acid rain? 238

Notebook Pages Go Here This is just a placeholder, replace these pages with your notebook pages when you submit on Gradescope. Submit as ONE PDF with notebook pages at the end. Report sheets must be submitted in the correct order or they will not be graded! Submit one pdf to gradescope with the report sheet pages in order and your notebook pages at the end. 239