My unknown compound is Questions 1. Why is it essential to (a) pack the sample tightly in the melting point tube and (b) heat the sample slowly and steadily as the melting point temperature is approached? 2. What is the effect of using too large a sample when determining a melting point? 3. Research chemists when determining the melting points of newly synthesized compounds often fill a second capillary tube with a known substance (of similar melting point range) and co-determine the melting points of the two substances using the same apparatus. What purpose does the determination of the melting point of the known substance serve? 4. For what two purposes are melting points routinely used? a. 5. b. Three test tubes contain white crystalline organic solids A, B and C, each of which melts at 149-150°C. A 50-50 mixture of A and B melts at 130-139°C. A 50-50 mixture of A and C melts at 149-150°C. In what range would a 50-50 mixture of B and C probably melt? What can you say about the identities of A, B and C? 10 © 2012 Cengage Leaming. All Rights Reserved. May not be scanned, copied or duplicated, or p