1- Benzoic acid(m.p 121 c ) is contaminated with 5% of 9,10-dimethylanthracene( m.p 1821 c ) . will the m.p of benzoic acid be above or below 121 c . why ?
2- two substance of practically equal solubility are present in the same amounts in a mixture . can they be separated by recrystallisation ? explain .
2006-09-19 17:07:17 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
1. Remember, freezing point depression. It is NEVER elevation! However, in real life you could be fooled if your mp unit is not calibrated correctly.
2. They cannot be separated by recrystallization in that specified solvent but may be able to be separated in another solvent. Also, you may be able to effect partial purification in a single crystallization but it would take multiple steps to get some pure and in the limit you would have zero product. This is the complex answer. From it you can deduce the simple answer you are probably looking for.
2006-09-19 17:35:50 · answer #1 · answered by gtoacp 5 · 0⤊ 0⤋
Melt benzoic acid and then drain it away from the dimethylanthracene (still solid)
Then recrystallize
Alternatively melt BOTH and recrystallize out the dimethylanthracene but I like the first method.
2006-09-20 00:19:12 · answer #2 · answered by Orinoco 7 · 0⤊ 0⤋
see as above
2006-09-23 06:28:17 · answer #3 · answered by Anonymous · 0⤊ 0⤋