Help identifying unknown chemicals.

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In summary, the conversation discusses the identification of 9 white solids. The solids include Aluminium ocide, Calcium Oxide, Sodium dithionite, aluminium sulphate, Ammonium sulphate, calcium nitrate, Magnesium sulphate, sodium carbonate, Sodium thiosulphate, and Zinc carbonate. The suggested method for identification is by determining the reactions of each solid with the given reagents, such as water, Hydrochloric acid, sulphuric acid, silver nitrate solution, ammonium hydroxide, and barium chloride. Creating a branching diagram can also be helpful in the identification process.
  • #1
I have 9 white solids which i need to identify. Aluminium ocide (Al2O3), Calcium Oxide (CaO), Sodium dithionite (Na2S2O4), aluminium sulphate ( Al2(SO4)3 ), Ammonium sulphate (NH4)2SO4, calcium nitrate ( Ca(NO3)2 ), Magnesium sulphate (MgSO4), sodium carbonate (Na2CO3), Sodium thiosulphate (Na2S2O3), Zinc carbonate (ZnCO3).

The reagents i have are: water, Hydrochloric acid, sulphuric acid, silver nitrate solution, ammonium hydroxide and barium chloride.

Any ideas on how to single a few out would be greatly appreciated!
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  • #2
Welcome to PF;
You want to start by fuguring what the reactions of each of them with each of the reagents would be.
i.e. do any of them look like they should dissolve in water?
  • #3
I find sometimes it is easiest to turn this into a branching diagram. You keep creating new branches until you are left with the one compound. Like Simon said, find out what they react with and go from there. Your first branch could be "Does it dissolve in water".
  • #4
A lot of those compounds are in materials databases - you can look up how they react with the different reagents.
Then it's mostly an exercise in logic.

Since it's been almost a month without feedback I guess the exercise is over and I wasn't really all that much help.
  • #5

I can suggest several methods for identifying the unknown chemicals provided. Firstly, a visual inspection of the physical properties of the solids, such as color, texture, and solubility, can help narrow down the possibilities. For example, aluminium oxide and calcium oxide are both white solids, but aluminium oxide is insoluble in water while calcium oxide is highly soluble.

Next, conducting simple chemical tests can help identify specific compounds. For instance, adding hydrochloric acid to a solid and observing the formation of bubbles indicates the presence of a carbonate compound, such as zinc carbonate. Similarly, adding silver nitrate solution can help identify the presence of chloride ions, which would be present in sodium chloride if it is one of the unknown solids.

Furthermore, conducting flame tests can help identify the presence of certain elements. For example, burning a small amount of the solid on a flame and observing the color of the flame can indicate the presence of sodium (yellow), calcium (red), or magnesium (bright white).

Another useful method is to perform qualitative analysis using reagents such as ammonium hydroxide and barium chloride. These reagents can react with specific compounds to produce precipitates or color changes, which can aid in identification.

In addition, performing spectroscopic techniques, such as infrared spectroscopy or mass spectrometry, can provide more precise identification of the unknown solids.

Overall, a combination of these methods can help narrow down the possibilities and identify the unknown chemicals. It is important to follow proper safety protocols and use appropriate equipment when conducting these experiments.

Related to Help identifying unknown chemicals.

1. What methods can be used to identify unknown chemicals?

There are several methods that can be used to identify unknown chemicals, including spectroscopy, chromatography, and mass spectrometry. Each method has its own advantages and limitations, so it is best to use a combination of techniques for more accurate results.

2. How do I determine the chemical formula of an unknown substance?

To determine the chemical formula of an unknown substance, you will need to know the mass and composition of the compound. This can be done through chemical analysis or using a mass spectrometer. Once you have this information, you can use it to calculate the empirical and molecular formula of the substance.

3. What safety precautions should I take when handling unknown chemicals?

It is important to always wear appropriate personal protective equipment (PPE) when handling unknown chemicals. This includes gloves, goggles, and a lab coat. You should also work in a well-ventilated area and avoid inhaling any fumes or dust from the chemicals. If you are unsure of the potential hazards of the unknown chemicals, it is best to work in a fume hood or consult with a safety specialist.

4. How can I determine the purity of an unknown chemical?

The purity of an unknown chemical can be determined through various methods, such as melting point analysis, titration, or spectroscopy. These techniques can help identify impurities in the substance and determine its purity level.

5. What resources are available for identifying unknown chemicals?

There are several resources available for identifying unknown chemicals, including online databases, reference books, and analytical testing services. You can also consult with a fellow scientist or a chemical supplier for assistance in identifying the unknown substance.

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