chemistry homework help 1

1. Draw on a separate and ungraded paper the Lewis Dot Structure of borane, BH3 and of phosphine, PH3, and list the bond angles. Then, draw the orbitals involved in bonding (valence orbitals) on the boron atom in BH3 and on the phosphorous atom of PH3­.  Label each orbital (for example: s, p, sp, sp2, or sp3).  In each case give the number of electrons that occupy these orbitals on B and on P.

 

Question: A reaction occurs between borane and phosphine involving an overlap of an occupied orbital on one molecule and an unoccupied orbital on the other. Considering your drawing, specify which orbitals are involved in this reaction.

 

2. Oleic and elaidic acid are both unsaturated fatty acids with the chemical formula C18H34O2. Look up the structures of these two fatty acids. Explain why elaidic acid is a solid at room temperature, but oleic acid is a liquid.

 

3. Imagine that you drive your car high in the mountains, where you have a minor accident.  The car airbag deploys, but instead of forming a large air pillow to cushion the driver, the airbag bursts open.  How can you apply the gas laws to explain what happened with the airbag?

 

4. Assuming that both diethyl ether (C2H5 O C2H5) and carbon dioxide (CO2) behave as ideal gases at 200°C, what mass of carbon dioxide would you need under the same conditions (200 °C in a 2 L container) to obtain the same pressure as you obtain from 7.4 g of diethyl ether? Show your work.

 

5. While neither diethyl ether nor carbon dioxide always behaves as an ideal gas, which of the two more closely resembles behavior of the ideal gas? Explain your answer considering the molecular structure and properties of the two molecules.

 

6. Compare two gas samples. Sample A: A 1 L sealed container filled with 0.060 moles of N2 at 400 K. Sample B: A sealed container at 6 atm with 0.020 moles of CO at 300 K.

 

How do the average speeds of the gas molecules in Samples A and B compare? Explain your answer.

 

7. A metal can filled with hot water vapor was closed with a rubber stopper and allowed to cool. After a few minutes, it imploded.  Explain why this happened using known properties of real gases.

 

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