Why Didn't Last 2 Test Tubes Dissolve?

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In summary, the conversation discusses the dissolving of benzoic acid in different solutions. While NH4OH, NaOH, and HCl dissolved the acid completely, NaHCO3 and diethyl ether did not. The concept of "like dissolves like" is questioned as all the solutions are polar. The basic dissociation constants of NaHCO3 and NH4OH are compared, with NH4OH being about 1000 times more basic. It is suggested to check the handbook for more information on why the bicarbonate ion did not neutralize the benzoic acid, and it is mentioned that benzoic acid may be too weak an acid to add a proton to the bicarbonate ion.
  • #1
MeatyDumplings
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i have 5 test tubes with benzoic acid, and i pour NH4OH, NaOH, HCl, NaHCO3 and diethyl ether into different tubes. The first 3 dissolved completely but the last 2 did not. Any ideas why?
i don't believe "like dissolves like" applies here since they are all polar.
 
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  • #2
I would be curious about how the basic dissociation constant of NaHCO3 compares to that of NH4OH. Check the handbook information. I'm not sure at the moment why the bicarbonate ion would not neutralize the benzoic acid; benzoic acid itself may be too weak an acid to add a proton to the bicarbonate ion. The Ammonia (solution in water) and the NaOH are both strong enough bases to neutralize the benzoic acid; and generally, Na+ salts and ammonium salts are soluble.
 
  • #3
[tex]K_B(NH_4OH) = 1.8\cdot10^{-5}[/tex]

[tex] K_B(HCO_3^-) = 2.3\cdot10^{-8}[/tex]

So NaHCO3 is about 1000 times less basic than ammonia.
Benzoic acid is a solid made of polar molecules, so it dissolves quite well in polar solvents as water and acetone and not in non-polar as diethyl ether.
 

FAQ: Why Didn't Last 2 Test Tubes Dissolve?

Why didn't the last 2 test tubes dissolve?

There could be several reasons why the last 2 test tubes did not dissolve. One possibility is that there was an error in the experiment, such as incorrect measurements or mixing of chemicals. Another possibility is that the substances used in the experiment were not meant to dissolve in the given conditions. It is also possible that the test tubes were made of a material that is resistant to the substances used in the experiment.

Is there a specific method for testing tube dissolution?

Yes, there are specific methods for testing tube dissolution. These methods may vary depending on the substances being tested and the conditions in which they are being tested. Some common methods include measuring the weight of the test tubes before and after the experiment, observing changes in the appearance or color of the test tubes, and conducting chemical tests to determine the presence of certain substances.

Can the experiment be repeated to see if the last 2 test tubes will dissolve?

Yes, the experiment can be repeated to see if the last 2 test tubes will dissolve. This is a common practice in scientific experiments, as it helps to ensure the reliability and validity of the results. If the experiment is repeated and the last 2 test tubes still do not dissolve, it may indicate that there is a flaw in the experimental design or setup.

Can the last 2 test tubes be dissolved by changing the conditions of the experiment?

It is possible that changing the conditions of the experiment may lead to the last 2 test tubes dissolving. For example, altering the temperature, pH level, or concentration of the substances used may have an effect on their ability to dissolve the test tubes. However, it is important to note that changing the conditions may also alter the results of the experiment, so it should be done carefully and with consideration.

How does the dissolution of test tubes relate to scientific principles?

The dissolution of test tubes relates to scientific principles such as solubility, chemical reactions, and intermolecular forces. Solubility is the ability of a substance to dissolve in another substance, and it is affected by factors such as temperature and pressure. Chemical reactions can also play a role in the dissolution of test tubes, as some substances may react with each other to form new compounds. Additionally, intermolecular forces, such as hydrogen bonding or London dispersion forces, can influence the dissolution of substances in a solution.

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