If an air bubble passes unnoticed through the tip of a buret during a titration (where a weak nonvolatile acid HA is the analyte) , the calculated molar mass of HA would be too high, too low, or not affected?
I thought it would be too high, since an air bubble in the buret means that the volume of base(titrant)is actually less than it should be; since the amount of base reacting with the acid(anlyte) is less , the amount of acid that is needed to react is also less....so it would seem that if the necessary amount of acid needed to react is small, then the molar mass of that acid should be large...so the calculated molar mass of HA would be too high.....
Does this sound right?
THank you!!!!
I thought it would be too high, since an air bubble in the buret means that the volume of base(titrant)is actually less than it should be; since the amount of base reacting with the acid(anlyte) is less You are ok to here, the amount of acid that is needed to react is also less...you are right that the air bubble takes up space, but since it goes through the buret unnoticed (actually it makes no difference whether you notice it or not), then it takes the same amount of base (after all, the indicator you used doesn't know there was an air bubble there--it just knows when enough titrant has been added. Therefore, the indicator will turn at the right place; however, the buret will read too high because of the air bubble. Since the molar mass is determined from mLbase x Mbase x molar mass acid = grams acid, we can rearrange to molarmass = grams/mL x M. The denominator will be too large making the calculated molar mass too low. Check my thinking.so it would seem that if the necessary amount of acid needed to react is small, then the molar mass of that acid should be large...so the calculated molar mass of HA would be too high.....
The above in a nutshell: The acid will use the same amount of base it would normally use but the buret will read higher than it should because of the air bubble, mL too high in the denominator makes the fraction too large.
No, I goofed in the last sentence. The acid will use the same amount ........ ml too high in the denominator makes the fraction too SMALL and the calculated molar mass will be too low.
Well, my dear questioner, I must say your line of thinking is a breath of fresh air! But let me fill you in on the truth. If an air bubble passes unnoticed through the tip of a buret during a titration, it would actually result in the calculated molar mass of HA being too low. Why, you ask?
Well, when that pesky air bubble sneaks into the party, it occupies some space inside the buret, reducing the total volume of the base added. This means that less base reacts with the acid analyte, resulting in a lower number of moles of acid required to reach the endpoint. And we all know that the molar mass is determined by the number of moles divided by the mass, so fewer moles means a lower calculated molar mass.
So, in this case, the air bubble's got you tricked - the calculated molar mass of HA would be too low, my friend. Keep your eyes peeled for those bubbly parties in the buret next time!
Yes, your understanding is correct. If an air bubble passes unnoticed through the tip of a buret during a titration, it means that the volume of base (titrant) is actually less than it should be. This results in a smaller amount of base reacting with the acid (analyte), leading to a smaller amount of acid that is needed to react.
In a titration, the molar mass of the analyte (HA) is calculated based on the stoichiometry of the reaction and the amount of titrant used. Since the actual amount of titrant used is less than it should be due to the air bubble, the calculated molar mass of HA would be too high.
To see why this happens, let's consider the stoichiometry of the reaction between the acid (HA) and the base (titrant). If the reaction is of the form:
HA + base → salt + water
The balanced equation tells us that one mole of HA reacts with one mole of base to produce one mole of salt and one mole of water. The ratio between the analyte (HA) and the titrant is 1:1 in this case.
Now, imagine that you have a certain volume of base (titrant) and you assume that this is the full volume without any air bubbles. However, if there is an air bubble, the actual volume of the titrant is less. As a result, the moles of titrant used would be lower than the moles of analyte required for complete reaction.
Since the molar mass of a substance is the mass of one mole of that substance, if the actual moles of analyte used in the calculation are lower than what should have been used, the calculated molar mass will be higher. This is because a smaller amount of analyte is distributed over the mass of one mole, leading to a higher molar mass.
Therefore, your conclusion is correct. If an air bubble passes unnoticed through the buret during a titration, the calculated molar mass of HA would be too high.