What possible errors can occur during titration that would affect calculations?

Answer 1

Titration is a common laboratory method of quantitative/chemical analysis which can be used to determine the concentration of a known reactant. Because volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the titrant, of known concentration (a standard solution) and volume is used to react with a measured quantity of reactant (Analyte). Using a calibrated burette to add the titrant, it is possible to determine the exact amount that has been consumed when the endpoint is reached. The endpoint is the point at which the titration is stopped. This is classically a point at which the number of moles of titrant is equal to the number of moles of analyte, or some multiple thereof (as in di- or tri- protic acids). In the classic strong acid-strong base titration the endpoint of a titration is when the pH of the reactant is just about equal to 7, and often when the solution permanently changes color due to an indicator.

Good accuracy requires that systematic errors be reduced as far as possible. The use of analytical grade reagents will reduce errors due to purity of reagents such as acid or alkali and the salt used for ionic background. Errors in temperature control are systematic errors. Electrode calibration error is also a systematic error, of particular importance when comparing duplicate titration curves.

Error in titre volume. The error in titre volume can be estimated by weighing. It is a good idea to check both the accuracy and precision of a burette. If the weight delivered at a given temperature is measures for a series of volumes the data can be fitted to a straight line; the required error value will then be given by the error on the slope.

Begin by preparing your buret, it should be conditioned and filled with titrant solution. You should check for air bubbles and leaks, before proceding with the titration to avoid error in volume.

Take an initial volume reading and record it in your notebook. Before beginning a titration, you should always calculate the expected endpoint volume. THis will help you to avoid errorsin recording the data, as it will be obvious if you end up with a massive difference.

Prepare the solution to be analyzed by placing it in a clean Erlenmeyer flask or beaker - you need to remove contamination to your results. If your sample is a solid, make sure it is completely dissoloved. Put a magnetic stirrer in the flask and add indicator.

Use the buret to deliver a stream of titrant to within a couple of mL of your expected endpoint. You will see the indicator change colour when the titrant hits the solution in the flask, but the colour change disappears upon stirring.

Approach the endpoint more slowly and watch the colour of your flask carefully. Use a wash bottle to rinse the sides of the flask and the tip of the buret, to be sure all titrant is mixed in the flask.

As you approach the endpoint, you may need to add a partial drop of titrant. You can do this with a rapid spin of a teflon stopcock or by partially opening the stopcock and rinsing the partial drop into the flask with a wash bottle. Ask your college to demonstrate these techniques for you, in the lab.

Make sure you know what the endpoint should look like. For phenolphthalein, the endpoint is the first permanent pale pink. The pale pink fades in 10 to 20 minutes.

If you think you might have reached the endpoint, you can record the volume reading and add another partial drop. Sometimes it is easier to tell when you have gone past the endpoint.

When you have reached the endpoint, read the final volume in the buret and record it in your notebook. paralax error, this is a personal error, in that you misread the scale, because your eye is not at a tangent to the liquid level.

Subtract the initial volume to determine the amount of titrant delivered. Use this, the concentration of the titrant, and the stoichiometry of the titration reaction to calculate the number of moles of reactant in your analyte solution.

Answer 2

Volumetric Analysis Titration Calculations

Answer 3

That depends highly on the kind of titration you're doing. Is it a volumetric or a gravimetric titration?

For volumetric titrations, the volume of sample can affect results if it's off by a couple mLs. For gravimetric, you are titrating MASS, so the volume is irrelevant.

You can make errors in the volume you deliver from your buret by the following means.
1) Your buret leaks (check the stopcock)
2) You incorrectly fill and/or read it due to parallax. (Parallax is an error that results when you look at the gradations on glassware from the wrong angle, or don't look at it from several angles. You visually misplace the meniscus and thus read it wrongly.
3). Bubbles in your buret or stopcock tip lower the volume actually present.
4). You may read the buret correctly but if you over- or undershoot your volumes (by inexperienced or incorrect use of the stopcock) you get errors that way.
5) Your sample volume is incorrect or inaccurate. (Some idiots measure liquid volumes INCLUDING their stirring bar, for example...)

See what other ones you can think of...

Answer 4

Personally, titrating isn't a hard thing per se...but some color changes happen gradually (I remember a clear to pink one that changed, changed back, add a bit more, get closer, change to pink, change back), etc. You can be a little sloppy there because you know the ultimate endpoint is coming.

Other ones though, a single drop of liquid can cause the color change/endpoint. If you are titrating too much/fast, you will totally miss it and your calcs will be very off.

So that's the answer in a nutshell....too much titrating and missing the endpoint.

Answer 5

Not viewing the meniscus horizontally is the main source of error.

Too fast a titration rate could cause you to overshoot.

Too strong a reagent and equally too weak a reagent can cause errors.

Poor lighting if you are looking for a subtle colour change.

Answer 6

Theres lots of potential error, you could accidentally go way past the equivalence point (when the amount of moles are the same), you could have some of your titrant stuck to the sides of your buret if not cleaned properly, so the volume you measure isnt accurate. The buret could dispense solution to fast into your beaker causing some of the substance to splash up on the sides, which changed the volume in it. You can have air bubbles in the tip of your buret if you dont dispense your titrant out properly before. etc.

Answer 7

Not have burette zeroed to start. Miss endpoint-go to far. Indicator old and not any good. Contaminated beaker or flask. Exact amount pipetted not correct -miniscus mis-read before titrate.

Answer 8

most of the time I mess up because I shoot way past the equivalence point-- since there's such a rapid change in pH, you can put too much in and throw it off.

then there's stuff like side reactions going on, imprecise measurements of molarity, volume, etc.

Answer 9

yes.. you might get a wrong PH because you are adding too much base to acid.. you might forget to write the volume of acid and base added together so that might also miss up the reaction... remember to keep track of volumes and as soon as you see the acid solution changing color .. do not add more base otherwise it will miss up the PH .. good luck