Chemistry

There are many types of pipettes (or pipet), but most are essentially a fancier version of a medicine dropper or eye dropper. They are used in a laboratory to transport and/or measure a specific volume of liquid.

Volumetric pipettes allow the user to measure a volume of solution extremely accurately and then add it so something else. They are commonly used to make laboratory solutions from a base stock as well as prepare solutions for titration. They typically only allow you measure one single volume in a particular size pipette (just like with volumetric flasks). Therefore, they come in many different sizes.

There are other types of pipettes also, such as a Pasteur pipette, which is not used to measure the volume of the liquid. It is essentially a large dropper, which can be used to remove liquid from one container and add it to another.

There are also graduated pipettes, also called a Mohr pipette, which also allow you to measure the volume of the liquid in the pipette, although not as accurately as a volumetric pipette. These use a series of marked lines (as on a graduate cylinder) to indicate the different volumes. These also come in a variety of sizes. These are used much like a burette, in that the volume is found by calculating the difference of the liquid level before and after.

All glass pipettes require the use of some kind of additional suction device, typically a pipette bulb (not the Eppendorf pipette or other similar ones, which have a built-in suction mechanism), which is a rubber bulb which sucks the liquid into the pipette and also allows you to drain the pipette in a controlled fashion. A Beral pipette is a one-piece pipette, usually made from flexible soft plastic (polyethylene) that has a built-in bulb on the end.

What is the importance of the "meniscus"?

The meniscus is the curve seen at the top of a liquid in response to its container. The meniscus can be either concave or convex. A concave meniscus (e.g., water in glass) occurs when the molecules of the liquid are more strongly attracted to the container than to each other. A convex meniscus (e.g., mercury in glass) is produced when the molecules of the liquid are more strongly attracted to each other than to the container. In some cases, the meniscus appears flat (e.g., water in some plastics).



Measure the meniscus at eye level from the center of the meniscus. In the case of water and most liquids, the meniscus is concave. Mercury produces a convex meniscus.

When you read a scale on the side of a container with a meniscus, such as a graduated cylinder or volumetric flask, it's important that the measurement accounts for the meniscus. Measure so that the line you are reading is even with the center of the meniscus. For water and most liquids, this is the bottom of the meniscus. Generally, you are measuring based on the center of the meniscus.

What is the proper technique for using these instruments?

This link should help: Pipetting Tips and Techniques

I will answer Part II later!

Hey Lena,

Pipette Techniques: See Attachment.

Bio_man

(a) What a burette is and how it is used in a titration (what is it used to measure?)

A buret is used to deliver solution in precisely-measured, variable volumes. Burets are used primarily for titration, to deliver one reactant until the precise end point of the reaction is reached.

Link: https://biology-forums.com/definitions/index.php/Buret

(b) what an indicator is and why it is used

An indicator is used to indicate when the end point of the reaction occurs, or when the reaction is complete. This can be an acid-base indicator such as methyl orange, which determines the end-point of a reaction with a colour change occurs.

Link: https://biology-forums.com/definitions/index.php/Indicator

(c) what tips are introduced regarding carrying out a successful titration

Hmm, check out the attachment and tell me if this is what you're referring to

(d) the specific types of calculations used in every titration. How did they determine the number of moles of NaOH that reacted with acid? How did they determined the number of moles of acid that reacted with NaOH? How did they then determine the concentration (in molarity, M) of the acid?

See the attached pictures for an example calculation...

(e) why the balanced chemical equation for the reaction you are performing is so important. Why do we need it with respect to our calculations?

Balancing provides the correct proportions when calculation; look at the step above (Find moles HCl)... it is 1 to 1. If we didn't balance it, say it was 2 to 1, then our calculations would be off.

A pipette is one of the laboratory instruments utilized in the transportation of a measured volume of fluids.  Therefore, the general use of a pipette is to transfer a specific volume of a fluid from one container (measuring cylinder) to another. There are several types of pipettes. They include; Volumetric, graduated, automated pipettes, micropipettes and disposable pipettes. But for the sake of the video, we will concentrate of two: Volumetric and graduated pipettes.
Volumetric pipettes
These pipettes are used to transport a single specific volume of a fluid, typically between 1 and 100 ml.  They are shaped like rolling pins with a huge belly, one blunted end (the neck) and one thinning end (the tip).  They are typically used for precise measurements, because they are intended to transport only one volume and are calibrated at that volume. They should be employed when accurateness and reproducibility are critical, since these can attain accuracy to four significant figures
Graduated pipettes
These pipettes are straight glass sometimes plastic tubes with one thinning end (the tip). They are usually calibrated into minute allotments in order that various quantities of liquid can be measured with the same pipette. They are usually utilized to compute any amount between 0.1ml and 25.0ml. They are not as accurate as volumetric owing to the fact that any deficiency in their interior diameter will have a larger effect on the volume delivered
Pipetting Techniques

The proper and best Pipetting method is forward Pipetting in opposition to reverse. In Volumetric pipettes, they ought to be packed to the point where the base of the meniscus of the fluid is at the stop line of the pipette. A pipette bulb is usually employed to draw fluid into the    pipette.  Subsequent to the pipette being filled, a finger is placed on the pipette and squirmed gently thus allowing the liquid to flow gradually to the fill line. Immediately, the pipette is packed to the fill line, the fluid can be transported to a container. A small amount of liquid will remain at the tip.
In graduated pipettes, in place of filling liquid to a fill line and transporting the total quantity, graduated pipettes are packed to a zero line and sapped to the mark of the preferred volume. For instance, to transport 2.00 mL of fluid, fill the pipette to the 0.00 mL mark, and drain to the 2.00 mL mark.

                                             Using a pipette

Methods among pipette users differ with setting, individual inclinations, and training. These disparities in implementation can influence the precision and the accuracy of results being released from a lab. To guarantee precision and uniformity, our laboratory has adopted a standard operating procedure for Pipetting techniques. We are inclined to use the volumetric pipette for chemical reactions.
Titration is a technique used to determine the concentration of solute contained in a known volume of solution by measuring how much of the solution is required to carry out a reaction. In any chemical laboratory, there are several titration techniques. They include Acid-base titration, Redox titration, Complexometric titration and Zeta potential titration, However, for the sake of this report, our main focus is on the Acid-base titration.
Acid-base titrations are rooted in the neutralization reaction that happens amid an acid and a base, when amalgamated. The acid solution is put to a burette. The base is as well added to a volumetric flask. The basic solution is habitually a standard solution of known concentration. The indicator used for such an acid-base titration often depends on the nature of the constituents.
In the video, the concentration of the acetic acid in vinegar was to be determined by neutralization using a known concentration of sodium Hydroxide. Since acetic acid (CH3COOH) and sodium hydroxide (NaOH) react in a known ratio, titration with a known concentration of sodium hydroxide can be used to determine the concentration of acetic acid in vinegar. In this reaction, the moles of sodium hydroxide were determined by multiplying volume (in liters) by the concentration. In this example, 35.42 mL of 0.502 M sodium hydroxide were required to neutralize the acetic acid in the vinegar. Since acetic acid and sodium hydroxide react in a one-to-one ratio, the moles of sodium hydroxide are equal to the moles of acetic acid. Dividing moles by volume of vinegar (20 mL) yields the concentration of acetic acid in vinegar (0.89 M CH3COOH).
Burette
A burette is a straight cylindrical laboratory instrument made of glass with a volumetric graduation on its full length and a precision tap on the bottom. It is employed to dole out known amounts of a fluid reagent in experiments for which such accuracy is compulsory.
Indicator
A pH indicator is a material used to indicate the equivalence point ,when the acid is completely neutralized by the base, through a color change. When the solution of vinegar, sodium hydroxide, and phenolphthalein just barely turns pink, the equivalence point has been reached.

I'm new but am asking the same question, I have only posted one time but am not able to open the tips you added Duddy. Thanks for any help my questions are:
There are specific types of calculations used in every titration. How did they determine the number of moles of NaOH that reacted with acid?
How did they determined the number of moles of acid that reacted with Na OH?
How did they then determine the concentration (in molarity, M) of the acid?

good jop

job*

*Smiles*
Just saying hi!
HI!
Mz

lol Don't mind if I do too!

Hello