1. An unknown substance,  is found to contain carbon, hydrogen and oxygen. It is a liquid with a fruity smell. Analysis show it to have the composition of 54.5% C, 36.3% O, and 9.1% H. At 100 C and 755 mm Hg, 188 ml of the vapor weighs .54 g.

a) Calculate the empirical formula of the substance ?

b) Calculate the molecular weight of the substance?

c) Propose a reasonable  structure of the compound? (Their are at least 4 possible answers.)

2. Match the group to the general formula:

___a) Alcohol A. RCO2H

 

__b) Alkene B. R-CH=CH-R

 

___c) Alkyne C. R2C=O

 

___d) Ketone D. RCH2-OH

 

___e) Aromatic E. R-NH2

 

___f) Acid F. R-CC-R

 

___g) Amine G. -C6H5

 


3. An unknown substance is found to contain 85.7% C and 14.3% H. At 100 C and 735 mm Hg pressure, the density of the substance is 2.21 g/L. When dissolved in hexane and Br2 added, no reaction occurs which means the compound does not contain pi bonds. a) What is the empirical formula of the compound? b) What is its molecular weight and its molecular formula? c) What is the structure of the compound?

4. The % composition of a phermone is 80.78% C, 13.56%H, and 5.66% O. 1.00 g of this compound dissolved in 8.5 g of benzene (Kfp = 5.12 o C/m) gives a freezing point depression of -2.13 o C. What is the empirical formula of the phermone? What is the molecular formula?

5.  Appendix D in your text gives the Ka's of Acetic, Oxalic, Chloracetic, Lactic, and Propionic Acids.  List structures (you can get these by googling their names) of these in order of their acidies and explain the acidities in terms of their structures.  (What groups withdraw electrons from the -O-H bond?  What groups donate electrons to the -O-H bond?)