Question

Lab Questions 1. Explain what happens to the moles of H" in the flask when you add boiled, deionized water to rinse the wall of the flask during the titration. Explain what happens to the moles of OH' needed from the buret to neutralize the acid after adding the water. What is the overall effect on the calculated acetic acid % of your sample? 2. Suppose that you do not add the water to rinse the wall of the flask, and several drops of base solution remain there. Explain what happens to the volume of base solution that you need to reach the endpoint. What is the overall effect on the calculated acetic acid % of your sample? 3. Deionized water absorbs CO2 when it is exposed to the air, and is boiled prior to this experiment to remove the CO2. CO2 is an acid, and is equivalent to H2CO3, so it creates H. Suppose your deionized water is not boiled. Explain what happens to the moles of OH' needed from the buret to neutralize the acid as a result. What is the overall effect on the calculated acetic acid % of your sample? 4. Suppose your solution has a very faint pink color. The intensity of the pink color at the endpoint is a function of the amount of what substance that you added to your solution? Explain whether or not you need to add more NaOH solution to make the color darker. What is the overall effect on the calculated acetic acid % of your sample if you do add more NaOH? 5. Suppose that you do not add the NaOH slowly and dropwise near the endpoint. Explain why this causes you overshoot the endpoint. Explain whether or not you can tell if you have passed the endpoint from the color of the indicator. What is the overall effect on the calculated acetic acid % of your sample?

Answer 1

1.

During the titration in between acid and bases sometimes we need take the help of water to clean the glassware, such as burette and conical flask. usually we take acid ina conical flask and base in to the burette. as water is the neutral medium it doesn't effect on the concentration of protons and hydroxyle ions.

2.

Suppose, we could not rinse the flask properly with distlled water after titration some drops of base over there in the flask.before doing another titration we will take some amount of acetc acid in the same flask where some drops of abse were there. these drops of base reatcs with acid . now we started adding base as usual from the burette but this time we will get the end point early comparing to the previuos titration.this causes error called human errors. these kind errors can be avoided.

3.

If deionized water was not boiled the levels of carbon dioxide remains the same the water. it produces the protons in the solution. this additional acidic strength will be added to the present acid called acetic acid in the flask. at this point of time the consumption of base will be more. this leads to incorrect calculation of strength of acitic acid percetage.

4.

Getting a dark pink color at the end point is not at all advisable. It means that we added excess amount of base to the acid. To get a good end point we should add base dropwise manner from the burette especially before the time of end point, moreover, we must stop adding base to the acid as soon as getting a pale pink color in flask. this indicates exactly the neutralization point.