CHEMISTRY ---&gt; why should only a few drops of indicator be used during any titrations

Titrations are searching for the point of neutrality where the acid exactly reacts with the alkali. Adding too much indicator can affect this balance and led to the this endpoint being found too early or later than if the neutralisation was due to just the other chemical you are titrating against.

So in short, too much indicator will affect the endpoint.

Reply 5

Tom H

9

Blobga

Another complete guess but wouldn't it throw the concentrations of the solution off

Nah, titrations don't depend on cocentration, just amount.

Reply 6

material breach

Tom H

Nah, titrations don't depend on cocentration, just amount.

That sentance is equally misleading, amount of what? Clearly concentrations and the amount you have of a solution are very important as togeather they tell you the amount of ions you are actually reacting.

Reply 7

Acid/base indicators are not pH neutral themselves. If you tip in loads of the stuff it will change the pH and you get an inaccurate reading.

Not guessing.

Marcus

Reply 8

Steeeeevo

15

anyone though of perhaps the simplest option? to save money? that’s what using small quantities boils down to most of the time in chemistry

Reply 9

Tom H

Nah, titrations don't depend on cocentration, just amount.

I disagree. Of course it depends on the concentration. If you take a flask of acid and then titrate against that, you will not get the same result as if you used half acid and half distilled water

Marcus

Reply 10

Steeeeevo

anyone though of perhaps the simplest option? to save money? that’s what using small quantities boils down to most of the time in chemistry

Not really, indicators and most common chemicals are relatively cheap. Mind you, I did use some deuterated solvents in an analysis of my product during my 3rd year project that cost several hundred pounds per 10ml and had to be carefully recovered and purified after use. I looked in Sigma-Aldritch and that wasn't even the most expensive one! So who thinks that printer ink is the most expensive liquid?

As an aside, for my opinion of the most expensive liquid chemical I would say di-tritium monoxide.

Marcus

Reply 11

Veles343

material breach

So in short, too much indicator will affect the endpoint.

Thats what I was told, add too much and it can throw off your accuracy

Reply 12

Ribbons

marcusfox

As an aside, for my opinion of the most expensive liquid chemical I would say di-tritium monoxide.

Marcus

just out of curiosity, HOW expensive is di-tritum monoxide (and what exaclty is it?!)

Reply 13

PSdilemma

just out of curiosity, HOW expensive is di-tritum monoxide (and what exaclty is it?!)

Well, you've heard of water. You've also heard of heavy water, with the second isotope of hydrogen. Tritium is the third isotope of hydrogen, (so it can replace the hydrogen in H₂O) and very rare. It is used in various self-luminescent devices, such as exit signs in buildings, aircraft dials, gauges, luminous paints, and wristwatches, but it's most significant use is as a triggering device for multi stage nuclear weapons. Cost of tritium itself is about $80,000 to £150,000 per gram.

Marcus

Reply 14

B Beth

A surplus of indictator will mess up the colours.

Adding a few drops of indicator to the acid/alkali will tell you what it is.

Reply 15

B Beth

Tritium being 80-150k per gram?! How on earth do they contain it?!

Reply 16

Mustard-man

18

amo17

the only idea that ive cum up with so far is that they might react with the alkali/acid. :confused:

Anyone care to correct me as this is just a mere guess and likely to be incorrect! :p:

saves money

Reply 17

B Beth

Tritium being 80-150k per gram?! How on earth do they contain it?!

Well, considering that the half life of tritium is only 12.3 years, they don't very well. It decays to ³He.

It is occurs naturally to the rate of one tritium atom to 10,000,000,000,000,000,000 hydrogen atoms and is created by nuclear reactions (on a very small scale, obviously) by cosmic rays in the atmosphere. N + ¹n => T (³H) + C.

It is manufactured commercially in nuclear reactors by neutron bombardment of ⁶Li. ⁶Li + ¹n => ⁴He + T (³H). The reaction is usually done with lithium fluoride in a vacuum and the tritium is allowed to diffuse through palladium. Tritium is actually a gas, the same as hydrogen is a gas, although T₂O is a liquid. There are more expensive radioisotopes, but they are generally all solids. Well, I suppose if you wanted to be pedantic, I guess you could always melt them.

Marcus

Reply 18

minnow2

5

marcusfox

I disagree. Of course it depends on the concentration. If you take a flask of acid and then titrate against that, you will not get the same result as if you used half acid and half distilled water

Marcus

But you add the indicator once the amount in moles of the substance has been accurately measured (by volume) into the flask. Therefore adding water or indicator at that point won't affect the titration in terms of altering volumes of concentration.Your analogy is flawed, the comparison should be "titrating against half a flask of acid" or "half a flask of acid topped up with half a flask of distilled water" both have the same "amount" (meaning moles) of acid in them.

Reply 19

Ribbons