Titration/Volumetric Analysis Lab

[FrankP]

This lab makes no sense to me. The information I am given and the information I am being asked are to abstract for me to figure out this early in my understanding of these concepts. Problem is Lab and Lecture are taught by different teachers at my school. My lab professor follows the book Lab 1-9 in order. Problem is my Chem Lecture professor does not. She teaches how she wants. We just learned molarity this week. We just started it no learned that's the wrong way to say it. I barely understand it and now I'm being asked to calculate these answers and I have no idea how to do it.

 

I'm going to scan this and attach it.

 

Here is whaIs known that may not be apparent from the pictures I added.

 

• NaOH we used 50mL of .1 M solution
• Diluted it to 500mL of NaOH solution with an unknown concentration

I can't figure out how to find moles of NaOH

 

My work so far:

 

I did (V₁)(C₁)=(V₂)(C₂)

• (50mL)(.1M)=(500mL)(C2)
• I got .01M NaOH

I know this calculation is right however the problem is in order to calculate the moles of NaOH I would have to know that the 50mL was exact which I can not prove that I got it as close to perfect as possible but i'm willing to bet it was at least .01mL off. Which the purpose of this lab is to figure out the values as specifically as possible so I don't want to guess...

 

My other question is that I set up a problem

Edited November 6, 2016 by FrankP

[studiot]

From this and your other question it sounds to me like your need to pay close attention to your lecturer.

 

She is right you need a crash course in stoichiometry, before you can progress in this stuff.

[FrankP]

From this and your other question it sounds to me like your need to pay close attention to your lecturer.

 

She is right you need a crash course in stoichiometry, before you can progress in this stuff.

 

I agree, however, I am not quite sure how your response is supposed to help me with my question. Suggesting I pay close attention is not why I asked the question. I'm a 25-year-old undergraduate student I am paying close attention trust me.

 

My question is specific I could use help with it, not suggestions on how to achieve academic success. I appreciate your input but would appreciate it more if I could get appropriate responses.

[hypervalent_iodine]

Some of what you've posted doesn't make a lot of sense.

 

• NaOH we used 50mL of .1 M solution
• Diluted it to 500mL of NaOH solution with an unknown concentration

For instance, what does this mean? Do you mean that you took a solution of NaOH (purported to be about 0.1M) and diluted it to 500 mL?

 

I can't figure out how to find moles of NaOH

Based on the image you scanned, the moles of NaOH comes from knowing the amount of the other thing you used in the reaction (potassium hydrogen pthalate; KHCH4O4). There is a reaction between these two species, so knowing the amount of one required for complete reaction will allow you to know the amount of the other thing.

 

My work so far:

 

I did (V₁)(C₁)=(V₂)(C₂)

• (50mL)(.1M)=(500mL)(C2)
• I got .01M NaOH

I know this calculation is right however the problem is in order to calculate the moles of NaOH I would have to know that the 50mL was exact which I can not prove that I got it as close to perfect as possible but i'm willing to bet it was at least .01mL off. Which the purpose of this lab is to figure out the values as specifically as possible so I don't want to guess...

 

This isn't how you calculate it. The whole point of this titration as far as I can tell is to standardise the NaOH. In other words, you assume the concentration is around 0.1M, but not exactly. I think perhaps you need to look up how simple acid base titration works and how we use it to standardise solutions.

[FrankP]

Some of what you've posted doesn't make a lot of sense.

 

 

For instance, what does this mean? Do you mean that you took a solution of NaOH (purported to be about 0.1M) and diluted it to 500 mL?

 

 

Ok yes sorry, this can be extremely unclear. I was able to figure this out using the suggestions. I have gone to my teacher's office hours as I usually do but rather than ask lecture based questions I decided to dedicate time to the lab. If you don't mind I will post my findings and let me know how I can become more efficient at obtaining this kind of information.

 

What I had meant was we added 50mL of .1M NaOH solution. We added approx. 450mL of water to dilute it. From there we performed a rough titration and 3 trial runs to standardize the concentration of the new 'diluted' solution of NaOH. From this, we performed 3 basic trial runs, bottled up the NaOH Substance with our names on it and stored it until today when we used that standardized substance to perform titrations on Vinegar & Anti-Acid tablets.

 

 

So the problem was from what I can understand was that the formula for the chemical reaction was not given. Since I am not good at creating chemical formulas out of thin air, (because we have not gotten to that part of my course yet) I was unable to identify that the mole ratio was 1:1.

 

I have also attached my sheet of work, where I (to the best of my abilities) worked out the solutions to my questions. I wanted to attach this work file as a way to redeem myself for asking such rudimentary questions.

 

[i know most if not all members of this forum are much more advanced on these topics. I feel a strong desire to get better at chemistry. Chemistry and physics are 2 of my favorite subjects I just lack formal education in it as it has been 10 years since my last chemistry class. So for that, I apologize I do want to advance my skill in the desired feild]

Edited November 8, 2016 by FrankP

[hypervalent_iodine]

There's no need to redeem yourself. Chemistry has quite a steep learning curve to it.

[FrankP]

There's no need to redeem yourself. Chemistry has quite a steep learning curve to it.

I have come to this realization. I am still determined to master my course but it is going to be quite the struggle. Thanks for the help again.