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Organic Chemistry Bonding

1. A sample of unknown Y is subjected to elemental analysis. The following percentages by weight are found to be:

C 40.0% H 6.7% O remainder of % by weight

The molar mass is found to be 60.0 g

A. Calculate the empirical formula (show work)

B. What is the molecular formula of unknown Y. (Include reasoning)

2. For the following compounds, draw the Lewis structures satisfying the octet rule. Show all the bonds and include any non-bonding pairs. Multiple bonds may be necessary in your final structures.

C3H8O C2H3CL

3. Refer to the following chemical equilibrium to answer the questions below:

CH3NH2 + HCOOH<-> HCOO- + CH3NH3+
pKa = 3.75 pKa = 10.56
(in water@25degrees C) (in water@25degrees C)

a. What is the Ka of HCOOH?
b. What is the base on the left side of the equilibrium?
c. What is the conjugate base on the right side of the equilibrium?
d. Which side of the equilibrium is favored?
e. What is the pKb of HCOOH?

Solution Preview

1. A sample of unknown Y is subjected to elemental analysis. The follwoing precentages by weight are found to be:

C 40.0% H 6.7% O remainder of % by weight

The molar mass is found to be 60.0 g

From this take 100 g of this substance....
40 g is carbon
6.7 g is hydrogen
53.3 g is oxygen
But we need a mole ratio...
40 g/12 g/mol = 3.3 mol
6.7 g/ 1g/mol = 6.7 mol
53.3 g /16 g/mol = 3.3 mol

This results in a mole ratio of C1H2O1 (empirical)
so we ...

Solution Summary

The chemical equilibrium questions are discussed. Calculations of empirical formulas, and molecular formulas can be seen in the solution. The solution contains the explanation of conjugate bases.

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