You can also get a very rough idea of the purity of your purified product from t
ID: 517344 • Letter: Y
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You can also get a very rough idea of the purity of your purified product from the melting point range. Give the melting point range for the purified product and briefly explain if these data give you any idea of relative purity of these two products. Give FOUR THINGS that you think you were supposed to learn about organic chemistry in this (and the first semester) lab course that you would not have learned in the lecture course alone, AND, also say if you actually learned them or not. There are NO CORRECT or INCORRECT answers to this question we are just curious what you think, you will receive 1 point for each of the four answers, anything you write is OK just so long as it looks like you took this problem SERIOUSLY.Explanation / Answer
16. The melting point is an important physical property of a compound. The melting point can be used to identify a substance and as an indication of its purity. The melting point of solid is defined as the temperature at which the solid exists in equilibrium with its liquid under an external pressure of one atmosphere.
A pure crystalline compound usually possesses a sharp melting point and it melts completely over a narrow range of temperature of not more that 0.5-1oC. The presence of even small amount of impurities usually produces a depression in the freezing points and shows a marked increase in the width of the melting point range. The melting point range of > 5oC indicates that the substance is impure. For a material whose identity is known, an estimate of degree of purity can be made by comparing its melting point with that of a pure sample.
Melting point depeneds on the factors like: (i) size of the molecule (ii) forces of attraction between the molecule .
Examples: The only force of attraction between butane molecules is weak Van der Waals force of attraction, so it has very low melting point. But in the case of methyl propionate, because of the presence of polar C – O group, the molecules are held together by dipole-dipole interaction. Therefore, its melting point is greater than that of butane. In the case of butyric acid, the molecules are held together by hydrogen bonding, so it has a higher melting point. The melting point of sodium butanoate is higher than that of butyric acid because the attractive force in sodium butanoate is strong ionic interaction.
17. Organic chemistry is a subject which provides more clarity if experimented in lab.
(1) Multi-step reactions can better understood in lab courses and not only in lecture course alone.
(2) There are many changes as the reactions proceeds, like color change or odour change which has a concept hidden in it and these concepts can be best understood in lab course.
(3) The better meaning of terminology can be understood if we practically learn them.
(4) Various apparatus that can be viewed as only images in lecture courses can be actually handled and perfectly understood in lab courses.
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