Question: Two substances, A and B, have the same melting point. how can you determine if they are the same without using any form of spectroscopy? Explain in detail.

My answer: Perform a mixture melting point. In this procedure, pulverize and mix A and B in equal quantities.. Then determine the melting point. If there is a melting point depression or if the range of melting is expanded by a large amount, you may conclude that one compound has acted as an impurity toward the other and that they are not the same compound.

Is this okay. Didn't know if it would work for two substances with the same temperature.

Sheryl

Yes, that's when it DOES work.
Remember delta T = kf x m
So if we have the same substance, then adding the two 50-50 produces no change, and delta T doesn't change because the melting point isn't depressed. But if the stubstances are not the same, then the molality changes, and delta T changes. In fact, if you know the molal freezing point depression and you know the amount of substances mixed (both of them), measurement of delta T will provide a molar mass. In this case, of course, since the identity of both A and B are not known, you would be required to use camphor or some other material and determine the molar mass of each separately.

Well, if you really want to determine if substances A and B are the same without using any spectroscopy, how about asking them? Just go up to A and B and ask them, "Hey, are you the same? Do you have a secret handshake or a special code word?" And if they both give you the same response, then you can conclude that they are indeed the same. But be warned, substances can be quite shy and might not respond, so you might need to add a little humor to get their attention.

In summary, performing a mixture melting point is a valid method to determine if substances A and B are the same without using spectroscopy. If the melting point remains unchanged and there is no depression or expansion of the melting point range, it suggests that the substances are the same compound. However, if there is a depression in the melting point or a significant expansion in the melting point range, it indicates that one compound is acting as an impurity towards the other, indicating that they are not the same compound.

Your explanation is correct, but I would like to provide some additional information to further clarify the concept.

To determine if two substances, A and B, have the same melting point without using any form of spectroscopy, you can perform a mixture melting point test.

Here's a detailed procedure:

1. Pulverize substances A and B separately into fine powders.
2. Take equal amounts of substances A and B (typically 50:50 ratio by weight or volume) and mix them thoroughly.
3. Place a small amount of the mixture into a capillary tube or a melting point apparatus.
4. Slowly heat the mixture, either using a Bunsen burner or a heating block, until you observe the first sign of melting.
Observe the temperature at which the mixture starts to melt.
5. Record the melting point of the mixture.

Now, let's analyze the results:

- If the mixture melts within a narrow range, around the same temperature as the individual melting points of A and B, it suggests that substances A and B are the same or highly similar. This is because the pure substances are mixing uniformly, and the overall melting behavior is similar to that of the individual substances.

- However, if the melting point of the mixture is significantly depressed or if a broad melting range is observed, it indicates that the substances A and B are not the same compound. The presence of impurities or differences in the composition between the two substances leads to the depression of the melting point or a wider transition range.

Keep in mind that the mixture melting point test is not always foolproof, especially if the substances have very similar melting points. In such cases, additional analytical techniques, such as spectroscopy or chromatography, may be required to confirm their identities definitively.

I hope this explanation helps! Let me know if you have any more questions.

Two substances, A and B, have the same melting point. How can you determine if they are the same without using any form of spectroscopy?