Biology Lab Does Sodium Chloride Reduce The Range Of The pH Change?

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timer Asked: Feb 13th, 2019
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Question Description

Please answer all questions on those photos in order.

The instructions for this assignment is located from page15 of the pdf.

Please make sure all your answer is accurate

While you are waiting… ØTurn in Lab 1 lab packet. ØRead the sample lab report at your bench. qNotice the order of every single page. qNotice the format (Paragraphs, not numbered statements) qNotice the content (includes more than just pH stuff) qCompare it to the “Lab Guidelines” on page 31. ØTake notes on what you see. ØDO NOT take pictures of it. ØDO NOT take it home qreturn it to me at the end of class The pH scale Ø pH = -log[H+] q [H+] of pure water is 10-7 M q pH = -log 10-7 = 7 Ø [H+] = 10-pH H+ H+ H+ + + H H + H H+ + + H H H+ H+ + H H+ H+ H+ H+ [H+] = 1 x 10-3 M q pH of blood is 7.4 q [H+] = 10-7.4 = 10-7.4 M pH = 3 (106 times more H+) Ø pH ranges from 0-14 H+ H+ [H+] =1x H+ 10-9 M H+ H+ H+ H+ pH = 9 Carbonic Acid - a buffer in blood Buffers are weak acids and don’t completely deprotonate i water. Carbonic acid Proton donor bicarbonate Proton acceptor HCO3− + H2CO3 H2CO3 Some molecules deprotonate H+ H2CO3 HCO3Some molecules stay intact. H+ H2CO3 HCO3- H+ H+ H+ HCO3H2CO3 HCO3- H2CO3 The following words are forbidden. Use of any of them in your lab report will lead to an immediate 2-point penalty. Acidic The words Acid and Base are still valid. Acidity Basic Basicity The use of these words in your lab reports will cause nothing but confusion and inaccuracies. The lab “Worksheet” must be filled out before you leave. Brief description of experiment: Controls and Experiment ØNon-buffer Control #1: qAdd acid to water and determine change in pH qAdd base to water and determine change in pH ØBuffer Control #2 qAdd acid to buffer and determine change in pH qAdd base to buffer and determine change in pH ØExperimental qAdd acid to NaCl and determine change in pH qAdd base to NaCl and determine change in pH Perform lab now. Ø Demonstrate pH meter. When you are done with Table 2-1 and 2-2… 1. Clean all glassware with tap water 2. Rinse all clean glassware with deionized water q From squirt bottle 3. Turn glassware upside down in drying rack 4. Refill squirt bottle with deionized water 5. Rinse pH meter probe. 6. Put a little pH 4 into probe cap 7. Cap the pH probe 8. Dispose of pipette tips. 9. Wash hands 10. Erase your table number from the board. 11. Finish filling out your worksheet. 12. Consult top of page 23 to learn how to do calculations necessary for table 2-3. Analyzing Lab 2 Data (page. ) Brief description of experiment: Putting together a “Lab Packet” 1.Before leaving lab. qAll primary data must be collected q“Worksheet” must be completed. 2.Do all required data analysis (secondary data) qcan be done during the lab or at home 3.Consult the lab packet’s Cover Page qdescribes what goes in your lab packet. qdescribes how lab packet will be graded. 4.Consult the Lab Report Guidelines qdescribes what we want in your typed lab report qorder of contents of your typed lab report How to use the “Lab Report Guidelines” to type up a lab report. Ø Found towards the end of each lab (page 31 for lab 2) Ø Provides a series of questions that must be addressed for each section of your lab report: q Introduction q Discussion q Conclusion Ø Use questions, in order, as a guide to write a cohesive paragraph for each section. Ø Be sure a reader who has never seen the questions can understand your paragraph. Example: Introduction of lab 2 Read the Lab Report Guidelines for the Introduction section of lab 2 on and see how they are used to make this paragraph. Introduction: pH is a measure of hydrogen ion concentration in an aqueous solution. Buffers are weak acids that minimize changes in pH of a solution. The current study focuses on sodium chloride, an ionic compound, and asks the question, is sodium chloride a buffer? Based on the fact that the chloride atom of sodium chloride can bind protons to make HCL, it was hypothesized that it is a buffer. This hypothesis will be tested by determining the change in pH of a sodium chloride solution after the addition of acid and base and comparing the results to those of a known buffer and non-buffer. Lab Report Pitfalls Avoid these in your lab reports The following words are forbidden. Use of any of them in your lab report will lead to an immediate 2-point penalty. Acidic The words Acid and Base are still valid. Acidity Basic Basicity The use of these words in your lab reports will cause nothing but confusion and inaccuracies. Failing to include question in answer. Ø1. What is your hypothesis? ØCorrect response in your lab report: qI hypothesized that NaCl is not a buffer. ØIncorrect response: qNaCl is not a buffer. Over-detailed Methods (in Intro) Ø…..after rinsing each beaker…. ØThree beakers were obtained and 50 mls of …… ØWe took the probe of the pH meter and used it to… ØDon’t discuss controls. Outcome is not Conclusion ØIf your prediction is… Ø “If I add acid to NaCl, I would expect to see a high change in pH relative to a known buffer. ØCorrect Outcome: qI did see a high change in pH after I added acid to NaCl. ØIncorrect Outcome: qThe outcome was that NaCl is not a buffer. Failure to use exact data. ØData from table: Fold change in [H+] = 101.8 ØCorrect usage in lab report: qThe total fold change in [H+] was 101.8. ØIncorrect usage in lab report: q The total fold change in [H+] was about 102. Failure to include raw data ØCorrect: qThe change in pH for sodium chloride upon addition of acid was 2.3 pH units which was much greater than that of the known buffer, which was 0.98 units. ØIncorrect: qThe change of pH for sodium chloride upon addition of acid was much greater than that of the buffer. Failure to compare data. ØCorrect comparison: qThe change in pH for sodium chloride upon addition of acid was 2.3 pH units which was much greater than that of the known buffer, which was 0.98 units. ØIncorrect comparison: qUpon addition of acid to sodium chloride, the pH change was 2.3 units, while that of the buffer was 0.98 units. Failure to discuss the correct data ØIf the lab manual says… q“How did the total pH change of sodium chloride upon the addition of acid compare to the buffer?” ØBe sure to discuss total pH change. Careful with your language. ØIncorrect q“We measured the absorbance of the beet cores under various conditions.” ØCorrect: q“We measured the absorbance of the solutions in which the beet cores were incubated under various conditions” ØIncorrect q“The wavelength was chosen to test 7 beet cores.” Proofread your Lab Reports! (or have someone proofread them for you)

Tutor Answer

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School: Boston College

Hello there, above is the completed assignment...

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Review

Anonymous
Tutor went the extra mile to help me with this essay. Citations were a bit shaky but I appreciated how well he handled APA styles and how ok he was to change them even though I didnt specify. Got a B+ which is believable and acceptable.

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