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What are some of the reasons for not using re-solidified sample for confirmation of melting point?
Wiki User
∙ 9y ago
I suppose that the crystalline structure was disturbed during melting and a new test on this sample may offer an erroneous result.
Wiki User
∙ 7y ago
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What is a capillary melting point?
The sample is placed in a sealed capillary and heated up to the melting.
How would you determine the purity of the solid crystals in crystallization?
One of the easier and more reliable ways to check if a solid compound is pure after re-crystallization is to check its melting point. Impurities will always lower the melting point of a sample, and the more impure, the lower the melting point will be. By checking the melting point of your sample with a reference value from a book or reliable internet source, it can be determined exactly how impure the sample is. If perhaps your compound is unknown, and thus are unable to obtain a reference value, you could obtain melting point of the sample, and then re-crystallize a few more times, obtaining a new melting point each time, until it is unchanged by re-crystallizing. This will of course decrease your yield, but if there is little fluctuation in your series of melting points, you can be sure you have a relatively pure sample.
Why is the melting point of a sample which has been previously melted different from the melting point of the original sample?
It depends on the elements in the molecules which make up the object, & how strongly those elements are bonded together.
Why will the observed melting point range be lower than true value if we heat the sample too fast?
A lower and wider melting point range could indicate that the sample was contaminated with trace amounts of impurities.
Which test or observation can be used to show that a sample of glucose is pure?
You could test its melting point, since pure glucose has a known melting point of 146oC.
What criterion is used for the purity of a sample of caffeine?
The closer the melting point of the sample of the caffeine you have extracted, to the known melting point of pure caffeine, the more pure your sample is.
What is a capillary melting point?
The sample is placed in a sealed capillary and heated up to the melting.
What properties could be used to help determine whether the sample is rreally zinc?
Melting point of the sample & Density of the sample
What is Sample of physical change?
For example melting of lead.
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How does the melting point of the crude sample compare with that of the purified sample?
An impure sample will have a lower melting point, and will also have wider melting point range than that of a pure sample of the same substance. a sharp melting point range can also indicate a eutectic mixture
Why is it important to determine the melting range of the impure and recrystallized sample of vanillin?
The melting point is an indication of purity.
How fast do you heat the sample when determining a melting point?
The apparatus used for determining the melting point will heat the sample at an appropriate rate. All you need to do is watch and note the point at which the sample melts, as should be demonstrated to you by your lab supervisor.
What is the term of melting point range?
The crystalline solids have a sharp melting point say 87oC but most of the amorphous solids do not have a sharp melting point they have a range of melting say they started melting at 87oC and continue till 89oC.
How does the melting behavior of lauric acid would change if an impurity was introduced in the sample?
An impurity lowers the melting point.
How would you determine the purity of the solid crystals in crystallization?
One of the easier and more reliable ways to check if a solid compound is pure after re-crystallization is to check its melting point. Impurities will always lower the melting point of a sample, and the more impure, the lower the melting point will be. By checking the melting point of your sample with a reference value from a book or reliable internet source, it can be determined exactly how impure the sample is. If perhaps your compound is unknown, and thus are unable to obtain a reference value, you could obtain melting point of the sample, and then re-crystallize a few more times, obtaining a new melting point each time, until it is unchanged by re-crystallizing. This will of course decrease your yield, but if there is little fluctuation in your series of melting points, you can be sure you have a relatively pure sample.
Why is the melting point of a sample which has been previously melted different from the melting point of the original sample?
It depends on the elements in the molecules which make up the object, & how strongly those elements are bonded together.
