Name: preparing standard solutions in the lab
Uploaded: 2024-12-05T18:31:54.000Z
Duration: 1 min 14 s
Channel: JoVE

Une solution standard est une solution dont la quantité de substance est connue avec précision. Il est préparé à partir d’un étalon primaire : une substance très pure, de masse molaire élevée, hydrophile et stable.
La préparation consiste à peser avec précision la quantité appropriée d’un étalon primaire dans un bateau de pesée et à la transférer dans une fiole jaugée à l’aide d’un entonnoir. Le bateau de pesée vide est pesé à nouveau pour vérifier s’il ne reste pas de substance solide.
Ajoutez de petites quantités d’eau distillée pour laver les solides dans l’entonnoir dans le ballon. La fiole jaugée est agitée pour dissoudre complètement le solide. Plus d’eau est ajoutée jusqu’à ce que son niveau atteigne près du repère d’étalonnage. À ce stade, l’eau est pipetée pour augmenter le niveau de solution exactement jusqu’au repère d’étalonnage.
Le ballon est fermé et retourné plusieurs fois pour assurer un mélange complet. Étiquetez le ballon avec la composition chimique, la concentration et la date de préparation.
Cette solution d’étalon primaire est utilisée pour normaliser les étalons secondaires, c’est-à-dire les substances moins pures et moins stables.

solutions étalons

Les solutions étalons désignent des solutions dont la concentration ou la composition est connue avec précision. Un étalon primaire est une substance stable, de masse molaire élevée et très pure, entièrement soluble dans l'eau, le solvant le plus couramment utilisé en chimie analytique. La solution étalon primaire peut être utilisée pour étalonner les étalons secondaires, qui sont des substances dont les concentrations sont connues mais qui sont moins pures et moins stables. Les solutions étalons sont essentielles pour obtenir des résultats précis et fiables dans les procédures analytiques. Il est donc essentiel de les comprendre pour toute personne travaillant en laboratoire.

La préparation d'une solution étalon à l'aide d'un étalon primaire comprend plusieurs étapes:

<ul style="list-style-type: disc; padding-left: 35px; margin: 0;">
	<li>Peser l'étalon primaire: utiliser une nacelle de pesée pour peser la quantité appropriée d'étalon primaire. Il est essentiel d'utiliser une balance capable de fournir des mesures précises.</li>
	<li>Transférer l'étalon dans une fiole jaugée: utiliser un entonnoir pour transférer soigneusement l'étalon primaire pesé dans une fiole jaugée propre et sèche. Assurez-vous que tout le solide est transféré de la nacelle de pesée à la fiole. Après le transfert, pesez à nouveau la nacelle de pesée vide pour confirmer qu'il ne reste aucun résidu.</li>
	<li>Lavez l'entonnoir: utilisez de petites quantités d'eau distillée pour rincer tout matériau solide de l'entonnoir dans la fiole jaugée. Cela garantit que tout l'étalon primaire est dissous dans la solution.</li>
	<li>Dissolvez le solide: faites tourner la fiole jaugée jusqu'à ce que le solide soit complètement dissous. Il peut être nécessaire d'ajouter de l'eau progressivement jusqu'à ce que le solide soit complètement dissous.</li>
	<li>Approchez-vous de la ligne d'étalonnage : ajoutez plus d'eau distillée pour amener le niveau de la solution près du repère d'étalonnage sur le col de la fiole jaugée. Assurez-vous que le solide est complètement dissous avant d'ajouter plus de solvant pour éviter de dépasser la ligne d'étalonnage.</li>
	<li>Ajustez le ménisque: utilisez une pipette pour ajouter de l'eau goutte à goutte jusqu'à ce que le bas du ménisque (la courbe à la surface du liquide) s'aligne précisément avec le repère d'étalonnage. Cette étape garantit que la solution a le volume et la concentration corrects.</li>
	<li>Mélangez la solution: fermez soigneusement la fiole jaugée et retournez-la plusieurs fois pour assurer un mélange complet de la solution.</li>
	<li>Étiquetez: étiquetez la fiole jaugée avec la composition chimique, la concentration de la solution et la date de préparation. Ces informations permettent d’identifier et d’utiliser correctement la solution.</li>
</ul>

Solutions étalons

Les solutions étalons font référence à des solutions dont la concentration ou la composition est connue avec précision. Un étalon primaire est un étalon très pur, une masse molaire élevée, ...

Education

Enseignement

JoVE Core

Analytical Chemistry

Chimie analytique

Unit 1

Unité 1

Method Development and Sampling Techniques

Développement de méthodes et techniques d'échantillonnage

method-development-and-sampling-techniques

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

Standard Solutions

preparing standard solutions in the lab

Standard solutions are prepared to have a precisely known concentration or composition. In analytical chemistry, this accuracy is important because it supports reliable results. A primary standard is a highly pure, stable substance with a high molar mass. It is fully soluble in water, which is the most commonly used solvent in analytical chemistry.

A primary standard solution can be used to standardize a secondary standard. Secondary standards have known concentrations, but they are usually less pure and less stable. This makes primary standards especially useful when exact measurements are needed in a laboratory setting.

The preparation starts by weighing the primary standard with a balance that gives precise measurements. The solid is then transferred through a funnel into a clean, dry volumetric flask. It is important to move all of the material from the weighing boat into the flask. The empty weighing boat is reweighed to confirm that no residue remains.

Next, small amounts of distilled water are used to wash any solid from the funnel into the volumetric flask. The flask is then swirled until the solid dissolves completely. More water is added gradually until the liquid is close to the calibration line on the neck of the flask.

The final volume is set by adjusting the meniscus, which is the curved surface of the liquid. A pipette is used to add water drop by drop until the bottom of the meniscus lines up exactly with the calibration mark. The flask is then closed and inverted several times to mix the solution well. At the end, the flask is labeled with the chemical composition, the solution concentration, and the preparation date.

Preparing Standard Solutions in the Lab

development of analytical methods

Analytical Methods: Technique to Protocol

Analytical methods follow a clear path from technique to protocol. In analytical chemistry, a technique is the scientific principle used to explain a chemical measurement. A method applies that technique to a sample of interest. The next steps are procedure and protocol. A procedure gives the directions for carrying out the analysis with an analytical method. A protocol is the detailed set of guidelines for that procedure, and it should be followed closely to get the desired results. <br...

quality control

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Quality Checks in Analytical Testing

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qualitative analysis

Classical and Instrumental Sample ID

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quantitative analysis

Measuring Analyte Concentration

Quantitative analysis measures the amount of a specific substance, called the analyte, in a sample. If the sample composition is unknown, qualitative analysis comes first. That step identifies the components so the correct substances can be measured during the quantitative phase. This method depends on two key measurements. Scientists measure the sample quantity and also a property that is proportional to the amount of analyte. Together, these measurements help determine the analyte...

instrument calibration

Calibrating Lab Instruments for Accurate Results

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glassware calibration

Calibrating Lab Glassware for Accurate Volume

Calibrating lab glassware helps students measure liquids accurately in the analytical laboratory. It reduces volume errors and supports consistent results across measurements. This matters when using volumetric flasks, pipettes, burettes, and other tools that depend on precise volume readings. Volumetric flasks are used to prepare aqueous solutions with a precise final volume. They have a calibration line on the neck. To calibrate one, fill it with distilled water until the meniscus, the...

standard solutions

Standard solutions are prepared to have a precisely known concentration or composition. In analytical chemistry, this accuracy is important because it supports reliable results. A primary standard is a highly pure, stable substance with a high molar mass. It is fully soluble in water, which is the most commonly used solvent in analytical chemistry. A primary standard solution can be used to standardize a secondary standard. Secondary standards have known concentrations, but they are usually...

blank solutions

Blank Solutions in Analytical Testing

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sampling methods: overview

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sampling methods: sample types

Sampling Materials in Solid, Liquid, Gas

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sampling plans

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sample preparation for analysis: overview

Preparing Samples by State and Form

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sample preparation for analysis: advanced techniques

sample-preparation-for-analysis-advanced-techniques

Preparing Complex Samples for Analysis

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sample handling

Sample Transport and Storage Basics

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contaminants and errors

Sampling Errors in Sample Preparation

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key terms and concepts

Learn how standard solutions are prepared from a primary standard using a volumetric flask, accurate weighing, meniscus adjustment, and proper labeling.

Preparing Standard Solutions in the Lab | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Preparing Standard Solutions in the Lab

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