ChemThreads SpotTest

How do you do it?

Identifying compounds:

Fill all but one well of the two first rows with a three drops of pure samples of the compounds that you suspect being in the unknown solution. Fill the empty well with distilled water.
Use the white paper to label each well.
Run the test on each well and analyse the results.
Fill a well plate with the unknown solution. Run different tests on each well. From the results obtained for each test, identify the compounds present in the solution.

Limit of detection:

Prepare a series of diluted solutions of the suspected compounds ( see dilution).
Filled each well with the different diluted solutions.
Used a white paper to label each well with the correct concentration and to label each row with the compound's name.
Run the test and analyse the results.

How do I analyze the results?

Identifying compounds: Use the results obtained from the tests run on the pure samples to identify the compounds of the unknown solution.

If this brown color appears when the thiocyanate test is run on the unknown solution, the solution contains Iron III ion.

What can I learn from it?

Identification of unknown compounds in a solution: Spot tests are very usefull to identify the different chemicals in a solution. However the experiment is long and errors can easily occur.

Limit of detection: A spot test can be used when looking for the lowest concentration of a chemical that a test can detect.

How do I analyze the results?

Limit of detection:

When the thiocyanate test is run on the unknown solution, it can detect iron III ion if the concentration of the ion is equal or higher than 10^-4 mol/L only.

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ChemThreads

ChemThreads is an educational tool designed to help students integrate their chemistry knowledge. The website is organized around six main threads: chemical analysis, chemical synthesis, chemical classifications, chemical architecture, chemical dynamics, and chemical reactivity. These thematic units have been chosen to organize the material around what we see as "big ideas" in chemistry.

Each of the threads is composed of a set of interconnected modules that address central concepts in the discipline. Within a module, you have access to: basic information on the module's topic, exploratory activities designed to foster your understanding of central ideas, a review quiz, concept maps to help you integrate your knowledge, useful simulations and other visualization tools, and links to related modules. Additionally, some modules allow you to access the module's content based on your level of understanding, from freshman to senior, helping you build connections between what you are currently learning in your chemistry classes and the ideas discussed in previous and future courses.

Chemthreads also offers a variety of resources that can help instructors implement interactive activities and group and individual projects in their courses (tools link).

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Chemthreads is organized in a series of inteconnected modules. Each module contains basic information for a given topic and most modules include a set of learning activities (review quizzes, explorations, applications).

There are several ways to navigate between different modules: highlighted text, nodes in a concept map, and the menus for related links and associated academic levels.

Overview

The particular chemical reactions used in a qualitative analysis scheme to confirm the presence of compounds are called spot tests.

A spot test experiment is typically done as follow. Solutions of known compounds are poured in the wells of a well plate. A specific test is run. From the reactions occuring in each well, one can identify what compounds the test identify. Therefore, when running the same test on the unknown solution, one can identify the chemicals present in the sample.

A sopt test can also be used to identify the limit of detection. It represents the critical concentration under which the reaction of the sample with the test may still occur but it is not observable. Typically, the sample is diluted and a set of different concentrated solutions of the sample is obtained. Each solutions is poured in a different well and the test is runed in each well. From the observable reactions, the limit of detection can be determined.

How do you do the experiment?

What do you need?

The materials needed are:

a well plate
white paper

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