Name:Essay Organic Chemistry

Name:Essay – Organic Chemistry

1. Consider the hydrocarbon pentane, C5H12 (molar mass 72.15g)
2. Write the balanced equation for the combustion of pentane to yield carbon dioxide and water.

1. What volume of dry carbon dioxide, measured at 25oC and 785 mm Hg, will result from the complete combustion of 2.50 g of pentane?

1. The complete combustion of 5.00 g of pentane releases 243 kJ of heat. On the basis of this information, calculate the value of ΔH for the complete combustion of one mole of pentane.

1. Under identical conditions, a sample of an unknown gas effuses into a vacuum at twice the rate that a sample of pentane gas effuses. Calculate the molar mass of the unknown gas.

1. Draw the structural formulas for all three isomers of pentane. Be sure to include all atoms of hydrogen and carbon in your structures.

1. In an experiment, a sample of an unknown, pure gaseous hydrocarbon was analyzed. Results showed that the sample contained 6.000 g of carbon and 1.344 g of hydrogen.
2. Determine the empirical formula of the hydrocarbon.

b. The density of the hydrocarbon at 25oC and 1.09 atm. is 1.96 g/L.

i. Calculate the molar mass of the hydrocarbon

ii. Determine the molecular formula of the hydrocarbon.

iii. To what family of hydrocarbons does this molecule belong? Name the molecule.

3.

1. For propanone, draw the complete structural formula (showing all atoms & bonds).

1. For propanone, predict the approximate C to C to C bond angle.

1. Explain why 1 - propanol and propanone do not have the same value for their standard heat of vaporization, ΔHovap, (You must include specific information about both compounds in each pair.)

Explain why propane and propanone do not have the same value for their standard heat of vaporization, ΔHovap, (You must include specific information about both compounds in each pair.)

1. Draw the complete structural formula for an isomer of propanone.

1. Given the structural formula for propyne below,

H

H –C – C = C – H

H

1. indicate the hybridization of the carbon atom indicated by the arrow.
2. Indicate the total number of sigma (б) bonds and the total number of pi (╥) bonds in the molecule.

4. Determine the empirical formula of a hydrocarbon that contains 85.7 percent carbon by mass.

1. The density of this hydrocarbon is 2.0 g L-1 at 50oC and 0.984 atm. Calculate the molar mass and the molecular formula of the hydrocarbon.

1. Octane, C8H18(l), has a density of 0.703 g mL-1 at 20oC. A 255 mL sample of C8H18(l) measured at 20oC reacts completely with excess oxygen as represented below.

2 C8H18(l) + 25O2(g)  16 CO2(g) + 18 H2O(g)

Calculate the total number of moles of gaseous products formed.

5.

The gas – phase conversion reaction between the geometric isomers cis-2-butene and trans-2-butene is represented above. The value of the equilibrium constant, Keq, for the reaction is 3.2 at 298 K and 1.0 atm.

1. In a mixture of the isomers at equilibrium at 298 K and 1.0 atm. Which is present at a higher concentration, cis – 2- butene or trans – 2- butene? Justify

1. If 1.00 mol of pure cis-2-butene and 1.0 mol of pure trans-2-butene were introduced into an evacuated container at 298 K, in which direction (to the right or to the left) would the reaction proceed to establish equilibrium? Justify

1. Given that Keq for the reaction at 400 K has the value 1.3, predict whether the reaction is endothermic or exothermic. Justify

1. There are other structural isomers of cis-2-butene and trans-2-butene. Draw one of these isomers, including all atoms, and give its IUPAC name.

6. Answer the following questions about a pure compound that contains only carbon, hydrogen and oxygen.

a. A 0.7549 g sample of the compound burns in O2(g) to produce 1.9061 g of CO2(g) and 0.3370 g of H2O(g).

i. Calculate the individual masses of C, H, and O in the 0.7549 g sample.

ii. Determine the empirical formula for the compound.

b. A 0.5246 g sample of the compound was dissolved in 10.0012 g of lauric acid, and it was determined that the freezing point of lauric acid was lowered by 1.68oC. The value of Kf of lauric acid is 3.90oC m-1.

i. Calculate the molality of the compound dissolved in the lauric acid.

ii. Calcualte the molar mass of the compound form the information provided.

1. Without doing any calculations, explain how to determine the molecular formula of the compound based on the answers to (a)(ii) and (b)(ii).

1. Further tests indicate that a 0.10 M aqueous solution of the compound has a pH of 2.6. Identify the organic functional group that accounts for this pH.

7. The structures for glucose, C6H12O6, and cyclohexane C6H12, are shown below.

1. Identify the type(s) of intermolecular forces in
2. pure glucose
3. pure cyclohexane

1. Glucose is soluble in water but cyclohexane is not soluble in water. Explain.