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7 Cards in this Set
- Front
- Back
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Coarse powders are not suitable for MP measurements because they do not pack very well and are far from neighboring molecules. |
To useful functions of knowing MP are the identity of substance, purity of a substance, distinguish compounds with similar MP |
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It is vital that the sample is heated slowly because then the temp recorder can have time to be accurate before melting starts. |
Two reasons why it's hard to measure temp at which crystals first begin to liquify are a) sweating of solvent still in sample, b) change in the sample shape due to heating, c) small amt of impurities are present so the liq produced is small & hard to detect. |
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2 effects soluble impurities have on the MP are low melting point and broad MP range. |
When crystals disappear rather than liquifying, sublimation is occuring. Liquid -> Gas |
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You should not heat organic solvents over a bunsen burner flame because it will be explosive. |
Activated Carbon should be added to a cool solution and not a boiling soln because C can induce boiling and cause the boiling soln to spill all over. |
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Oiling out occurs when the MP of the solute is higher than the BP of the solvent. As a result, compound is deposited as an oil & not crystals. |
A seed crystal can be placed in the flask for crystal growth and scratched glass gives sites for crystal formation. |
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Activated Carbon have a surface area that adsorbs dissolved organic substances. |
Heat the receptacle beaker so the resulting vapor will help avoid crystals from forming in the funnel |
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the thermometer head should be placed just below the junction of the flask with the liquid to be distilled and the distillation column. This way, the temperature of the vapor, not the liquid is being measured. The vapor is what is actually being cooled and collected in distillation, not the liquid. |
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