Pre Lab Question Please answer in complete sentences. Describe the characteristi
ID: 1024117 • Letter: P
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Pre Lab Question Please answer in complete sentences.
Describe the characteristics of a good recrystallization solvent The solubility of a compound is 59 g per 100 mL in boiling methanol and 30 g per 100 mL in cold methanol, whereas its solubility in water is 7.2 g per 100 mL at 95 degree C and 0.22 g per 100 mL at 2 degree C. Which solvent would be better for recrystallization? Explain why. In what circumstances is it necessary to do a hot filtration What is an appropriate heating rate during the determination of a melting point? What happens if the rate is faster? What happens if it is slower?Explanation / Answer
a) the characterization of good solvent are
(i)
b) as discussed in above point (1), the solubility of compound should be high in hot solvent and very low in cold solvent.
As 30g / 100mL is as good solbility as 59g /mL so we cannot use methanol as solvent
However the solubility at 95C is high enough (7.2 g / 100mL) while it is sparingly soluble at 2C
c) we use hot filteration if the impurities are soluble in hot solvent while the compound to be purified is insolbule in hot solvent.
d) the recommended melting point rate is 1-2 degrees per minute
If the rate is high, then there is ample possibility that we may miss the exact melting point and also the melting range of compound will be more broad.
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