Pre-lab Experiment Acid-Base Titration Prof. Pinar Alscher | Lab Reports Chemistry

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Pre-lab Experiment 20-Acid-Base Titration: Standardization of KOH and Determination of the

Molarity and/or Percent Composition of an Acid Solution

Recording your data anywhere except in your book will result in penalties of the worst kind.

Calculations go in the calculation section, not in the observation section

Format & Clarity of the Report: See lab report checklist. (Handout #6)

Before class starts: Read the lab for the week carefully before you start writing your pre-lab. The purpose

and procedure should be neatly written in your lab book before class starts. Pre-lab questions need to be

correctly answered.

Spacing: You will need 1 pages for the purpose & pre-lab. The procedure usually takes about 2 pages.

Leave space, you are collecting a lot of data. You have at least 6 data trials. Data tables will use 1page. Most

students need 2 pages for calculations. The results table is short and will only use 0.5-1 page. The questions

are about 2 pages.

Purpose: Address the following in your purpose: What will you ultimately determine in this lab? Each step

has you determine some value or an observation leads you to a conclusion, but not all observations and

calculations are suitable for the purpose.

Introduction: None, write the METHOD here. Summarize the steps for the lab.

Pre-lab questions: Pre-lab questions are designed to help you do the lab. Put your pre-lab questions after

the METHOD and before the PROCEDURE. You should thoughtfully answer the questions clearly and

concisely using complete sentences, good grammar, and in Standard English. The answers should be easy to

read and follow. They will serve as a reference for YOU when you do your calculations for lab. The answers

should address the main thrust of each question.

(Remember, ALWAYS show your work and explain your reasoning.)

1. What would happen to the standard solution concentration if water was inadvertently introduced?

2. Should the reaction vessel be dry?

3. Once the mass of the vinegar is known, is it okay to add water to the reaction vessel?

4. What is the purpose of a titration?

5. What is an indicator used for? (You might need to use the index in your textbook.)

6. What is the difference between an endpoint and an equivalence point?

7. Calculate the approximate mass of KHP you will need to weigh out to make 250 mL of 0.10 M KHP

solution. The formula of KHP is KHC8H4O4.

8. In Part 1, when you are making the solution of KHP, why can't you use a spatula or scoopula to

transfer the KHP to the flask?

9. In Part 1, when you are adding water to the KHP, why must you start over if you add a little too

much water?

Procedure Notes:

Part 1: Make your solution carefully. Do not go over the mark on the neck of the flask. Transfer this

solution to a clean, dry 250-mL Florence flask (To distinguish between an Erylenmyer and a Florence flask,

remember: My aunt Florence has a round bottom!)

Part 2 & 3: The instructions for the titration process is the same for both parts.

You will use one burette in these titrations. Rinse your burette with base three times before using it. Put

white paper under the reaction flask when doing a titration so that you can see the color change. Use 1-2

drops of indicator to visualize the endpoint. Use the same bottle of indicator for each trial. During the

titration, be sure to rinse the walls of the titration flask with distilled water. KEEP YOUR BASE

SOLUTION UNTIL EVERYONE IN CLASS IS DONE WITH THE EXPERIMENT. WE USUALLY

NEED EXTRA BASE.

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Pre-lab Experiment 20-Acid-Base Titration: Standardization of KOH and Determination of the Molarity and/or Percent Composition of an Acid Solution Recording your data anywhere except in your book will result in penalties of the worst kind. Calculations go in the calculation section, not in the observation section Format & Clarity of the Report : See lab report checklist. (Handout #6) Before class starts: Read the lab for the week carefully before you start writing your pre-lab. The purpose and procedure should be neatly written in your lab book before class starts. Pre-lab questions need to be correctly answered. Spacing: You will need 1 pages for the purpose & pre-lab. The procedure usually takes about 2 pages. Leave space, you are collecting a lot of data. You have at least 6 data trials. Data tables will use 1page. Most students need 2 pages for calculations. The results table is short and will only use 0.5-1 page. The questions are about 2 pages. Purpose: Address the following in your purpose: What will you ultimately determine in this lab? Each step has you determine some value or an observation leads you to a conclusion, but not all observations and calculations are suitable for the purpose. Introduction: None, write the METHOD here. Summarize the steps for the lab. Pre-lab questions: Pre-lab questions are designed to help you do the lab. Put your pre-lab questions after the METHOD and before the PROCEDURE. You should thoughtfully answer the questions clearly and concisely using complete sentences, good grammar, and in Standard English. The answers should be easy to read and follow. They will serve as a reference for YOU when you do your calculations for lab. The answers should address the main thrust of each question. (Remember, ALWAYS show your work and explain your reasoning.)

What would happen to the standard solution concentration if water was inadvertently introduced?
Should the reaction vessel be dry?
Once the mass of the vinegar is known, is it okay to add water to the reaction vessel?
What is the purpose of a titration?
What is an indicator used for? (You might need to use the index in your textbook.)
What is the difference between an endpoint and an equivalence point?
Calculate the approximate mass of KHP you will need to weigh out to make 250 mL of 0.10 M KHP solution. The formula of KHP is KHC 8 H 4 O 4.
In Part 1, when you are making the solution of KHP, why can't you use a spatula or scoopula to transfer the KHP to the flask?
In Part 1, when you are adding water to the KHP, why must you start over if you add a little too much water? Procedure Notes: Part 1: Make your solution carefully. Do not go over the mark on the neck of the flask. Transfer this solution to a clean, dry 250-mL Florence flask (To distinguish between an Erylenmyer and a Florence flask, remember: My aunt Florence has a round bottom!) Part 2 & 3: The instructions for the titration process is the same for both parts. You will use one burette in these titrations. Rinse your burette with base three times before using it. Put white paper under the reaction flask when doing a titration so that you can see the color change. Use 1- 2 drops of indicator to visualize the endpoint. Use the same bottle of indicator for each trial. During the titration, be sure to rinse the walls of the titration flask with distilled water. KEEP YOUR BASE SOLUTION UNTIL EVERYONE IN CLASS IS DONE WITH THE EXPERIMENT. WE USUALLY NEED EXTRA BASE.

Do the titrations at least two [ 2 ] times/per person in the group. Allow space in your procedure area for the initial volume of acid, the initial and final volumes of base used, and any other data. In total, each group should have no less than 6 titrations. More is better The better results for this lab are obtained when the analytical balance is used for mass measurements. You will do as many titrations [at least 6] as you need to be within 1.5% agreement. Do this calculation on scratch paper. You can transfer it to your calculation section later. Read the burette to 0.00mL. Make sure that there are no leaks or air bubbles in the burette tip. Part 2: Collect your base in a DRY 500 mL Florence flask. Part 3: You need the mass of the vinegar for each trial. Qualitative Observations/Data Collection: In lab, you will make observations and collect data. You should pay appropriate attention to details in the lab. What color did the solution turn? How many milliliters of solution did I use? The observations and data collection are specific to the steps. Calculations go in the calculation section EVEN IF THE MANUAL TELLS YOU TO DO A CALCULATION IN A PARTICULAR SECTION. SO, UNLESS I SAY SO, only data and observations go in the observation section. This also includes balanced equations or information that infers a conclusion. All data is included and labeled clearly. All significant figures and units are correct. The appropriate numbers of trials were done for each section in the lab. Data collection needs to be done with care, use this section to look beyond the obvious observations: Record any observations, errors, or difficulties that came up when carrying out the procedure (did not use an analytical balance, misread the burette, missed the endpoint, added more than one drop of indicator, did not rinse the sides down with distilled water) Note: You read the burette down. The burette shows the volume delivered into the flask not the volume contained in the burette. Watch for a drippy stopcock. This is a source of error. Make sure that all the glassware is primed with the solution that you will use for the lab. The burettes are primed with base. Data (collected in the observation section): For this experiment: Part 1: you should have recorded in the mass of the KHP; Part 2 the volume of base solution delivered for each titration, the burette reading before and after each titration, the volume of KHP solution used. Part 3: The volume of base solution delivered for each titration, the mass of the empty Erlenmeyer flask, the mass of the flask with vinegar, the type, brand, and acidity of the vinegar. Data Tables: Below are examples of data tables for this lab. TABLE EXAMPLES. THEY DO NOT REPRESENT THE NUMBER OF TIMES YOU REPEAT THE TRIALS. READ THE PRE-LAB. Part 1: Preparation of Standard KHP solution Mass of KHP Part 2: Standardization of Base Trial 1 Trial 2 Final volume base Initial volume base Volume of base used Part 3 : Determination of mass percent and molarity of a vinegar solution Mass of Erlenmeyer and vinegar

time to think about the quality of your answer. (No credit if you did not show your work or explain your reasoning). The answers should address the main thrust of each question. Answers involving calculations should have the correct significant figures and units. IF YOU PUT YOUR PRE-LAB QUESTIONS IN THE QUESTIONS SECTION, YOU WILL LOSE 50% OF THE POINTS FOR THAT SECTION. IT TELLS ME YOU DID THEM AFTER THE LAB WAS DONE. Points will be deducted for circular reasoning, not clearly addressing the question, errors in math, sigfigs, units, and exponential notation. (No credit if you did not show your work or explain your reasoning.) you will lose points for answers that are written on binder paper.

In Part 1, if you used a scoopula to transfer the KHP out of the vial and some solid stuck to it, how would it affect your result for MKHP? (Would the calculated (wrong) MKHP be higher or lower than the actual MKHP ?)
In Part 1, if you added a little too much water to the volumetric flask, would the calculated MKHP be higher or lower than the actual MKHP?
In Part 2, if there was an air bubble in the tip of the KOH buret that came out during the titration, how would MKOH be affected? (Would the calculated MKOH be higher or lower than the actual MKOH ?)
Why is it acceptable to add water to the titration flask?
Why can't you add water to either solution at any time before they are transferred to the titration flask?
If 25.00 mL of a sulfuric acid solution (H 2 SO 4 ) is titrated with sodium hydroxide, and if it requires 35.88 mL of 0.1127 M NaOH to reach the equivalence point, what is the molarity of the sulfuric acid solution?
A sample of 0.495 grams of solid KHP is weighed into an Erlenmeyer flask. This sample is titrated with a sodium hydroxide solution, and 28.56 mL of NaOH are required to reach the endpoint. The sodium hydroxide solution is then used to titrate a sample of phosphoric acid of unknown concentration. It requires 29.88 mL of NaOH to react with 10.33 mL of H 3 PO 4 solution. What is the concentration of the phosphoric acid?
A 2.353-g sample of vinegar was titrated with 0.08751 M NaOH, and it requires 22.31 mL of NaOH to reach the endpoint. Calculate the mass percent of acetic acid (HC 2 H 3 O 2 ) in the vinegar sample. 𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 =

Pre-lab Experiment Acid-Base Titration Prof. Pinar Alscher, Lab Reports of Chemistry

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