Introduction
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.
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 or 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 pipettes 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 put 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.
Meniscus
This is the arc observed on top or bottom of a fluid in reaction to the container holding it. A meniscus can be either curved in or curved out. When an idividual interprets a level on the surface of a container, for example a graduated container, it's significant that the calculation makes up for the meniscus.
Part Two: Titration
This is a method employed to establish the concentration of solute enclosed in an identified volume of solution by gauging how much of the solution is essential to perform 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 a neutralization reaction which happens an acid reacts with a base solution. The acid solution is put in a burette. The base is as well put in a volumetric container. The basic solution is habitually a standard one that is of known concentration.
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 with a volumetric graduation on its length and a accuracy 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.
Tips introduced regarding carrying out a successful titration
The main tips that are introduced in the video about carrying out a successful is following instructions. It is imperative for anyone carrying out this experiment to be very careful and follow the instructions relayed in the laboratory manual. The instructions will help out greatly.
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?
In chemistry, A mole symbolizes 6.02 x 10^23 molecules of a specific compound. Moles are therefore written in accordance with the average mass of a gram. For instance, if a substance is 8 g when a mole is weighed, subsequently the compound will have 8 grams per mole as a molar.
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).
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 accurate percentages when calculation. For example on the above reactions, the ratio is 1:1. If we did not balance it, say it was 2 : 1, and then our calculations would be off. Balancing ensures accuracy.
Definitions
(a) Burette
A burette is a straight cylindrical laboratory instrument with a volumetric graduation on its length and a accuracy tap on the bottom. It is employed to dole out known amounts of a fluid reagent in experiments for which such accuracy is compulsory.
(b) End point
This is the point upon which a pH indicator changes color. This indicates that the acid has neutralized the base.
(c) Titration
This is a method employed to establish the concentration of solute enclosed in an identified volume of solution by gauging how much of the solution is essential to perform a reaction.
(d) Hydrogen ion
The positively charged ion of hydrogen, H+, fashioned by elimination of the electron from atomic hydrogen.
(e) hydroxide ion
The ion OH-, characteristic of basic hydroxides.
(f) Neutralization reaction
This is a chemical reaction wherein an acid and a base react with the development of a salt.
(g) Molarity
The molar concentration of a solution.
(h) pH
This is measure of the acidity or alkalinity of a solution.
(i) Titration curve
Is a curve in the plane whose x-axis is the titrant’s volume added since the commencement of the titration, and whose y-axis is the concentration of the base.
References
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