lab report on DETERMINATION OF PERCENT KHP AND ACID EQUIVALENT WEIGHT

  

DETERMINATION OF PERCENT KHP AND ACID EQUIVALENT WEIGHT 

Titration is a process of mixing measured volumes of reacting solutions in such a manner that one can determine when chemically equivalent amounts of reactants are mixed. One of the purposes of the titration process is to determine the concentration of a solute in a solution. Additionally, the titration process will be used in the analyses of soluble solid unknown acids. 

The equivalence point of a titration is the point at which stoichiometric amounts of reactants have been mixed. A method must be used to show when the equivalence point has been reached. In acid-base titrations, phenolphthalein is often used as an indicator. Phenolphthalein is an organic molecule that is colorless in acidic solution and pink to red in the presence of base. If the indicator is placed in an acidic solution it will be colorless. As base is added to this solution, a pink color develops as the neutralization (equivalence) point is passed. 

In this experiment each student will work alone and: 

a. prepare an approximately 0.1-M NaOH solution. 

b. standardize (precisely determine the molarity, ±0.0001 M) the NaOH using the pure solid monoprotic acid standard, potassium hydrogen phthalate (KHP). 

c. determine the percent by mass of KHP in an impure sample. 

d. determine the mass of a solid acid unknown that neutralizes one mole of hydroxide ion. 

e. prepare a formal write-up of the experiment. 

potassium hydrogen phthalate, (KHP) 

Note: You will need to prepare your own data tables for this experiment. These will be turned in as part of the formal lab report. These tables must be prepared before you come to lab to begin data collection. You need to make sure that all measurements made have a place in the data tables (i.e., initial buret reading, final buret reading, etc.)

PROCEDURE 

A. Preparation of an NaOH solution 

1. Thoroughly clean your large screw cap bottle. Also clean its cap. 

2. Review calculations for dilution and calculate the amount of 6-M NaOH needed to prepare 500 mL of approximately 0.1-M NaOH. 

3. Using the 6-M NaOH in the hood, measure out the calculated amount of NaOH (use a graduated cylinder) and place it in the clean screw cap bottle. 

4. Fill the bottle to the 500 mL line with distilled water (this is approximately 500 mL). 

5. Cap the bottle and mix well by inversion (at least 20 inversions). 

6. Put your name and/or locker number on the bottle of NaOH. 

7. For this experiment you will need to create your own data tables. Read through the procedure (Parts B, C, and D) and create data tables for recording your data in the days to follow. You must have places in your data tables for all data taken in the procedure. 

B. Standardization of NaOH solution 

Note: The NaOH you have prepared is approximately 0.1-M. You must determine the precise molarity of your NaOH to at least 4 significant figures (keeping only the number of significant figures allowed). 

1. Obtain and clean the buret assigned to your lab locker according to the signs posted in the lab. Rinse it 3 times with 2-3 mL of your NaOH solution prior to filling it. If you wish to use a beaker or funnel to help fill your burette you must clean them and then rinse them with your NaOH solution prior to their use. Clean a 250 mL Erlenmeyer flask (it does not have to be dry). 

2. Fill the burette with your NaOH solution, rinse solution through the burette tip to eliminate air bubbles, and note the initial burette reading to two decimal places. 

3. Obtain a capped vial of pure potassium hydrogen phthalate (KHP), standard. Label this vial and keep it capped when it is not in use. 

4. Calculate the mass of pure KHP (molar mass = 204.23 g mol-1) that will require about 20 – 25 mL of approximately 0.1-M sodium hydroxide solution for complete reaction. Remember that KHP is monoprotic. 

5. Do one trial. Take the vial of pure KHP, your clean flask, and the data sheet to the analytical balance room and measure KHP into the flask. Use the approximate mass (+/- 0.05 g) calculated in step 5 as a guide. Record the precise mass of KHP dispensed into the flask to the nearest 0.0001 g. 

6. Dissolve the KHP in the flask in about 50 mL of distilled water. 

7. Add 2 to 3 drops of phenolphthalein and titrate the flask to a consistent very, very faint pink end point. Record the final burette reading and calculate the total volume of NaOH used for the titration. The contents of the flask can now be discarded. (Save your KHP for additional trials.) 

Note: If your titration volume was at least 10.00 mL (4 significant figures) this titration can be included in your calculations. However, a larger titration volume (closer to 25 mL) will give better precision. On the other hand, an unnecessarily large titration volume (more than 25 mL) is time consuming. The volume of NaOH solution required is directly proportional to the mass of KHP titrated. If the volume for your first your titration was not between 20 and 25 mL, adjust the mass used for the rest of your trials. 

8. Clean three 250 mL Erlenmeyer flasks (they do not have to be dry) and label them #1, #2, and #3. 

9. Take the vial of KHP, your 3 flasks, and your data sheet to the analytical balance room and measure KHP into each of the 3 flasks using the first trial as a guide. Record the exact mass of KHP in each flask to the nearest 0.0001 g. 

Note: You should refill the buret for each titration. The NaOH solution remaining in your buret at the end of each lab session should be saved in a clean dry beaker and used for rinsing the buret at the next lab session. Never put unused solution back into your stock bottle. You risk contaminating your NaOH solution. 

10. Follow steps 7 and 8 for each of your flasks. 

11. Use the volume of NaOH solution and the mass of KHP in each flask to calculate the molarity of your NaOH. (You will need to average at least 3 values.) 

12. Determine and record the average molarity of your NaOH. This solution will be used to determine the values for your unknowns. Take good care of it!! 

13. Using at least three molarity values calculate your percent relative average deviation (see Appendix A at the end of this lab manual). Note: Percent relative average deviation is a measure of precision and at least 3 trials are required for the calculation to be meaningful. If your average deviation is less than 2%, it means that the data you have collected shows good precision and you have completed enough trials. If it is greater than 2%, then additional trials are needed. 

C. Determination of percent KHP in an impure sample 

1. Clean, rinse, and fill the buret with your NaOH as you have done for previous titrations. 

2. Obtain a clean, dry capped shell vial containing an impure KHP unknown. Record your unknown’s number and label the vial. Keep this vial in your locker until your graded lab report has been returned to you. 

Note: The shell vial of unknown contains enough sample for at least six trials. No additional unknown will be provided! Should an unknown be spilt, a different unknown will be obtained and you will start that unknown’s analysis from the beginning. 

3. Do one trial titration with the unknown using about twice as much mass as was used for pure KHP. Record the precise mass of unknown (±0.0001 g) and volume of NaOH used (±0.01 mL). (Titration procedure is exactly the same as that used previously.) 

4. You will need to do at least two more trials. If the total volume of NaOH used in your first titration was less than 20 mL use a little more unknown for your subsequent titrations. If your titration volume was greater than 25 mL use a little less unknown. (The mass of impure KHP and the volume of NaOH solution used in the titration are directly proportional). 

5. Calculate the percent by mass of KHP in your impure sample for each trial. 

6. Determine the percent relative average deviation using the calculated mass percents from all your trials. Do additional trials if your deviation is greater than 2%. 

7. Report the average percent by mass of KHP for your unknown. 

D. Determination of the mass of an unknown acid required to neutralize one mole of Hydroxide ion. 

1. Obtain a clean, dry capped shell vial containing an impure KHP unknown. Record your unknown’s number and label the vial. Keep this vial in your locker until your graded lab report has been returned to you. 

Note: the shell vial of unknown contains enough sample for at least six trials. No additional unknown will be provided! Should an unknown be spilt, a different unknown will be obtained and you will start that unknown’s analysis from the beginning. 

2. Do one trial titration using between 0.1 to 0.4 g of the unknown acid. Be careful!! It is easy to dump in too much solid. Titrate as before. 

3. If your initial titration volume is less than 20 mL use a little more unknown. If your titration volume was greater than 25 mL use a little less unknown. (The mass of acid and the volume of NaOH solution used in the titration are directly proportional.) Do at least two more trials. 

4. For each trial, calculate the mass of your unknown acid required to neutralize one mole of hydroxide ion. 

5. Using the calculated mass of acid/mole OH- values, determine the percent relative average deviation. Do additional trials if your deviation is greater than 2%. 

6. Report the average grams acid/mole hydroxide neutralized for your unknown. 

E. Write a formal lab report. Carefully follow all of the instructions or you will lose points. 

1. The report does not need to be typed, but must be legible, neat, and secured in a folder so that it does not fall out. 

2. Use only one side of each piece of paper. 

3. The report must contain the following labeled sections in this order: 

a) Title page: A page with only the identifying title of the experiment, your name, and the date the report is submitted. 

b) Introduction: a paragraph (be concise) describing what values you have been asked to determine in the experiment, (not how to do the experiment). Include the balanced chemical equation for the reactions used in parts B and C of this experiment. No numbers should be used in this part of your report.

c) Procedure: Do not repeat the details of the procedure given in your lab book or you will lose credit. Instead, you should write several paragraphs summarizing the theory of the procedures you used in your experiment. Some of the topics these paragraphs should cover are: What is a titration? What is a buret (maybe a sketch would be useful) and how is it used? What is the “equivalence point” in an acid/base titration? How do you know when you have reached the “equivalence point?” How is the “equivalence point” different from the “end point?” What is an indicator (in general) and what is phenolphthalein (the specific indicator used in this experiment)? No data should be presented in this part of your report. 

d) Data tables: Present all of your data in neat, table form. All measurements must be included. 

e) Sample calculations: Show at least one complete sample calculation for each type of calculation. 

f) Results: Report your unknowns’ numbers and the average values you obtained (not the relative average deviation) for each unknown. Put nothing else in this section. 

g) Error discussion: Your error discussion should first define systematic and random errors. Then it should give definitions of accuracy and precision. Now make sure your error discussion answers the following questions: Which type of error, systemic or random, affects accuracy (and the grade on your unknowns)? Which type of error affects precision (and your percent relative average deviation)? What are some possible systematic errors that could occur in this experiment? What are some possible random errors that could occur in this experiment? How would each of the possible errors in this experiment affect your results? What can be done to try to minimize each type of error? 

NOTE: The Introduction, Procedure, and Error discussion of this lab report should be in complete sentences, paragraph (not outline) format and will be graded for spelling and grammar as well as content. Be sure to reference any outside sources that you used to write your report.

ACID BASE PAPER

  

A) Compare and contrast weak bases and strong bases.

B) Discuss oxidation-reduction reactions.

  

C) Compare and contrast weak acids and strong acids.

Discuss each of the following topics, your response for each should be 200 words in length and use scholarly sources in the APA style.

John Muir Edmund Burke

As requested:

 

Background: John Muir (1838-1914) was a naturalist, writer, and an early advocate of preserving America’s natural resources for future generations. His writing was instrumental in the foundation of the National Parks System.

 

First steps: This paper is a combination of research and rhetorical analysis. Use the library to do research on John Muir, and the National Park system. Using Edmund Burke’s Of the Sublime and the Beautiful, look at John Muir’s writing about the Yosemite and see where he has used Burke’s thinking about the sublime in his writing.

 

Write: In your introduction, you will give some background on John Muir’s development of the National Park System and how he wrote articles to interest people, and then move into a rhetorical analysis of how he used the concept of the sublime in his writings, and what persuasive techniques were used. In this last part you will be quoting and paraphrasing Muir and Burke. Talk about who Muir’s intended audience was and how that influenced his technique, tone, and word choice.

 

 

Make sure you have a clear thesis, and that you support it with quotes and specific information properly cited. Review the handouts on thesis development posted on Moodle.

 

*NOTE very important:

 

you may use this link ONLY as reference, you may rephrase but not copy his work

 

https://www.dropbox.com/s/etmm6c3zv5l9lw2/Johnmuir.doc

Chemical Bonding

Chemical Bonding

Provide an explanation for three of the twelve items below.

a.  Explain how valence electrons create a chemical bond, and how they are obtained.

b.  Explain the difference between an ionic bond and a covalent bond.

c.  Provide the number of valence electrons in each structure.

1.    Cl2

2.    O2

3.    N2

4.    PI3

5.    CCl4

6.    HONO2

7.    Hl

8.    PH3

9.    CS2

10.HOCl

11.CH3OH

12.HOCN

3 pages due in 18 hours

Titration Lab-Finding Ka
In this lab you will use an online titration simulation to determine the Ka of two hypothetical weak acids.

Step 1: Plan your Lab

Write out a purpose, procedure and materials list that you would need if you were going to complete this experiment in a conventional lab. Be sure to include safety considerations in your procedure! You will want to visit the simulation at http://users.wfu.edu/ylwong/chem/titrationsimulator/index.html to “look around” and get a feel for the materials available.

Step 2: Conduct your Inquiry

Visit the page: http://users.wfu.edu/ylwong/chem/titrationsimulator/index.html and select Find the Ka of a hypothetical weak acid solution from the list (menu option 3)

Conduct your inquiry on two different acids (you can select the “restart with a new unknown pKa” to test the second acid. If you would like to re-run a titration of the same acid, make sure you select “restart using the same unknown concentration” (there is a typo).

Record your observations: in this case you will take a screen shot (use the print screen function on your computer which can then be pasted into a word document) of

The initial set up of the experiment (as shown below) AND
the finalized titration curves with the answers present (after you have pressed the “turn in lab report button”

These are to be included with your report (a minimum of 4 pictures in total-2 for each acid tested).

Each picture must have descriptive title below it. See the following example:

Figure 1: this figure shows the experimental set up using 0.1M NaOH to determine the pKa of an unknown acid in a 25ml solution.

Step 3: Find Ka and Concentration

Using the data you have gathered, calculate the Ka value for each hypothetical acid.

Once you have calculated your Ka value, use the data to find the concentration of the unknown acids. You will need to submit this work with your lab.

Step 4: Applications of Titrations

Write a paragraph explaining at least one application of titration in the real world. If you use external information, this information must be cited using in-text citations (Smith, 2010) AND referenced using a full reference. Note that this is worth a large portion of your mark and must be sufficiently detailed and insightful to get those marks!

Testing completed by the school psychologist indicates that Joe is intelligent and creative. Results do not support the presence of a learning disability or a developmental disability. The school psychologist indicates that Joe lacks sufficient motivation or desire to complete his work thoroughly or carefully. Joe’s parents report that he refuses to follow rules at home, is often angry, and tends to blame his siblings when he gets into trouble.

A Logician’s View: Deducion, Induction, Fallacies

PLEASE IF YOU DONT HAVE THE ACCESS TO THE BOOK, DO NOT BID ON IT.

MANDATORY Reading Required Materials: 

Current Issues and Enduring Questions: A Guide to Critical Thinking and Argument, with Readings 10th Edition 

ISBN-13: 978-1457622601 

ISBN-10: 1457622602 

Ch. 9: “A Logician’s View: Deducion, Induction, Fallacies

Answer the following in 250-300 words.

Below are some fallacies in action. Identify the logical fallacies, some may only have one, for each scenario. Explain what has gone wrong in the fallacies. Be specific in your reasoning.

1.DeLay argues that stem-cell research is immoral. But DeLay is an ultra right-wing lunatic who’s incapable of thinking objectively. Obviously his argument is non-sense.

2.Barbara Striesand, Paul Newman and Julia Roberts are Democrats. Therefore all Hollywood stars are Democrats.

3.Smirnoff is the best vodka available: renowned violinist Pichas Zukerman says, “When it comes to vodka, Smirnof plays second fiddle to none.”

4.If a car breaks down on the freeway, a passing mechanic is not required to stop and provide road service. Likewise, if a person has a heart attack on the street, a passing physician is not obligated to render emergency medical care.

5.When water is poured over a pile of rocks, it always trickles down to the very bottom. Similarly, when rich people make lots of money, we can expect this to trickle down to the less fortunate.

6.Aborion is murder—and it doesn’t matter whether we’re talking about killing a human embryo or a human fetus