Would my calculated molarity of HOAc in vinegar be too high, low, or unchanged if
a) i forgot to rinse wet buret with vinegar
b)delivered vinegar into a wet flask
c)used a buret with a broken tip
Any help please!!!
I assume from the problem that you have used vinegar as the titrant and a primary standard OR the know molarity of a base such as NaOH.
HOAc + NaOH ==> H2OP + NaAc.
moles NaOH = L x M = ??
moles HOAc = samae
M HOAc = moles HOAc/L HOAc.
a) So if you did not rinse the buret with HOAc before using it and the buret was wet, then you must add MORE volume (it will take a higher volume because some of what you are adding from the buret is water) so the M will be too low (the denominator is too large).
b. Delivering HOAc into a wet flask, along with the base, will have no effect. That is because the water contains no moles of either base or acid. My students always got confused with that answer and they kept telling me that "we were diluting the HOAc." My answer was, "Tha't right, and we are diluting the base by the same amount."
c. There is no definitive answer for (c) because there are several scenarios; however, the best guess is that we would overshoot the end point which means L HOAc is too high which makes M HOAc too low. But if you were very careful, did not allow a full drop to form before it fell into the titrating flask but allowed just a small amount out of the broken tip before washing it off OR better touching the tip to the titrating flask, I think you could get a good titration and the M HOAc should be ok.
a) If you forgot to rinse the wet buret with vinegar, your calculated molarity of HOAc in vinegar would be too low. Why? Well, imagine the wet buret as a clingy ex, holding on to some of its previous substance. These remnants can dilute the HOAc, making it seem less concentrated than it actually is. So, remember to give that buret a good rinse next time!
b) If you delivered vinegar into a wet flask, your calculated molarity of HOAc in vinegar would be too high. Why? Because the wet flask can act like a thirsty sponge, guzzling up some of the vinegar and reducing its overall concentration. It's like your vinegar is having a wild party in the flask, but some of the guests are too absorbed in the wetness. So, dry that flask, my friend!
c) If you used a buret with a broken tip, your calculated molarity of HOAc in vinegar would be unchanged. However, your ability to accurately measure the volume of the liquid may be compromised. Picture the buret as a clown with a broken nose - it can still do its job, but it may not be as accurate or reliable. So, it's best to fix that broken tip or get a new buret for precise measurements.
a) If you forgot to rinse the wet buret with vinegar, the calculated molarity of HOAc in vinegar would be too low. This is because any liquid residue remaining in the buret from a previous experiment could dilute the vinegar, leading to a lower concentration of HOAc in the solution.
b) If you delivered the vinegar into a wet flask, the calculated molarity of HOAc in vinegar would be too high. This is because any liquid residue in the wet flask could add extra volume to the solution, leading to a higher concentration of HOAc.
c) If you used a buret with a broken tip, the calculated molarity of HOAc in vinegar would be unchanged. The broken tip would not affect the concentration of the acetic acid in the vinegar solution itself. However, it might affect the accuracy of the volume measurements taken during the titration process.
To accurately determine the effect of different factors on the calculated molarity of HOAc in vinegar, we need to understand the process for determining molarity and how these factors can influence the results. Here's a step-by-step guide to determining the molarity of HOAc in vinegar using a titration method:
1. Set up the experiment:
- Obtain a buret and ensure it is clean and dry.
- Rinse the buret with vinegar to remove any residual impurities.
- Set up a clean and dry flask to receive the vinegar solution.
2. Perform the titration:
- Fill the buret with a standardized sodium hydroxide (NaOH) solution, whose molarity you know.
- Record the initial volume (V1) of NaOH solution in the buret.
- Add a specific volume of vinegar to the flask using a pipette.
- Add a few drops of phenolphthalein indicator solution to the flask. The indicator will change color when all the acetic acid in the vinegar reacts.
- Slowly add NaOH solution from the buret into the flask while stirring continuously until the color of the indicator permanently changes. Record the final volume (V2) of NaOH solution in the buret.
3. Calculate the molarity of HOAc in vinegar:
- Determine the volume of NaOH solution used (V2 - V1).
- Use the balanced chemical equation for the reaction between acetic acid (HOAc) and sodium hydroxide (NaOH) to determine the mole ratio.
- Calculate the number of moles of NaOH used.
- Determine the number of moles of acetic acid (HOAc) present in the vinegar using the mole ratio.
- Finally, calculate the molarity of HOAc in vinegar by dividing the number of moles of HOAc by the volume of vinegar used.
Now, let's analyze the impact of each of the given factors on the calculated molarity of HOAc in vinegar:
a) If you forgot to rinse the wet buret with vinegar:
- In this case, the residual water in the buret could potentially dilute the vinegar solution when it is added to the buret.
- As a result, the volume of NaOH solution required to neutralize the acetic acid might be higher.
- Consequently, the calculated molarity of HOAc in vinegar would appear to be lower than the actual value.
b) If you delivered vinegar into a wet flask:
- When you added vinegar to a wet flask, the water present in the flask might mix with the vinegar, effectively diluting the acetic acid solution.
- Consequently, a larger volume of NaOH solution would be required to neutralize the acetic acid.
- As a result, the calculated molarity of HOAc in vinegar would appear to be lower than the actual value.
c) If you used a buret with a broken tip:
- If the buret's tip is broken or damaged, it can result in an irregular flow rate of NaOH solution during titration.
- The irregular flow rate could lead to inaccuracies in the volume measurements and potentially affect the calculated molarity.
- The calculated molarity of HOAc in vinegar could be either higher or lower, depending on the specific circumstances.
It is worth noting that these factors might have a relatively small effect on the final calculated molarity, especially if the manipulated volumes are significantly smaller than the measured volumes. However, it is generally best practice to minimize or avoid these factors to ensure accurate results.