You are asked to determine the thermometer correction for your assigned melting

Question

You are asked to determine the thermometer correction for your assigned melting point apparatus. You obtain a pure sample of benzoic acid and determine its melting point range carefully. After several trials, you obtain a very sharp melting point of 115.8 degrees celsius. What is the thermometer correction at this temperature? For purposes of these questions, the melting point of very pure benzoic acid is 122.4 degrees Celsius. (The thermometer correction is the value that must be added to the observed thermometer reading. You have to type in your answer with a + or - sign. )

In a recrystallization of benzoic acid, you begin with a sample of 4.00 grams. After several recrystallizations, a dry sample of 2.7 grams was obtained experimentally. What was your percent recovery? (The format of your answer is important, e.g. 33.2 percent would be entered as 33.2 without any percent symbol or the word percent.)

Explanation / Answer

The thermometer correction is the value that must be added to the observed thermometer reading

Actual melting point of pure benzoic acid =122.4 degrees Celsius

thermometer reading=115.8 degrees celsius

thermometer correction=122.4-115.8=6.6

This value is to be added to the thermometer reading

percent recovery=(mass recovered/sample used)*100=(2.7/4.0)*100=67.5

percent recovery=67.5

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