Project #33868 - Chemistry

1.      The development of MRI imaging technology is one useful spinoff of basic research into the structure of the atom. Research, however, is expensive. Many people argue that the high cost of research outweighs its potential benefits. Provide one argument for and argument against increasing current funding for atomic-structure research. Use specific examples from this lesson in your answer to support each position. (6marks)

2.      The emission spectrum of an unknown element contains two lines one in the visible portion of the spectrum, and the other, ultraviolet. Based on the figure below and on what you have learned about Niels Bohr’s model of the atom, account for the difference in energy between these lines. (3 marks)

3.      a) Draw the energy-level diagram and write the electronic configuration for zirconium (element 40). (3 marks)          

 

b) Use the diagram to explain why the Zr4+ ion exists. (2 marks)

c) Compare the stability of the Zr atom and the Zr ion. Account for any differences in their stability. (2 marks)

4.      Draw an orbital overlap diagram to represent the bonding in ammonia, NH3. 

(5 marks)

5.      Draw the Lewis structure and structural formula for:

a)      HCN

b)     SO3 2-

(8 marks total)

6.      Experimental evidence suggests that the nitrogen atom in ammonia, NH3, has four identical orbitals in the shape of a pyramid or tetrahedron.

a)      Draw an energy-level diagram to show the formation of these hybrid orbitals (Hint: No electron promotion is required.) (4 marks)

b)     Name the type of hybrid orbitals found NH3. Of the four hybrid orbitals on the N atom, how many will take part in the bonding? Explain. (2 marks)

c)      Draw the energy-level diagram showing the hybrid orbitals formed in the C atom when it bonds. Looking at those hybrid orbitals and those of the N atom, describe how the bonding with a N atom will differ with the bonding that occurs with a C atom, even though both atoms have four hybrid orbitals oriented in a tetrahedral shape. (2 marks)

7.      a) Calculate the differences in electronegativity between the elements in each of these compounds. (3 amrks)

i)                    CaBr2

ii)                  Na3N

iii)                CH4

b)     Predict whether each of these compounds would be an ionic or a molecular compound and justify each prediction. (3 amrks)

c)      Rank the bonds in these compounds in order of decreasing ionic character. Where do we always find compounds containing metals, in this ranking order? (2 marks)

8.      For the ion IO3 -,

a)      draw the electron dot diagram and structural formula. (4 marks)

b)     predict the shape. (1 mark)

c)      predict whether it is polar or non-polar, and justify your prediction. Indicate the positive and negative poles. (2 marks)

9.      For the molecule CHCl3

a)      draw the electron dot diagram and structural formula. (4 marks)

b)     predict the shape. (1 mark)

c)      predict whether it is polar or non-polar, and justify your prediction. Indicate the positive and negative poles. (2 marks)

10.  The molecular shapes of water and methane are based on sp3hybrid orbitals attached to the central atoms. Why are the bond angles in these molecules not identical? (2 marks)

11.  Imagine that you are the owner of a small dry-cleaning business that is considering switching from using the “normal” organic solvents to liquid carbon dioxide, as described in the lesson introduction.

a)      Provide a brief explanation of why carbon dioxide is a suitable solvent to use. (2 marks)

b)     Research two pros and two cons of using liquid carbon dioxide for dry cleaning. (2 marks)

12.  Consider the following boiling point data for these halogen molecules.

Substance

Electrons

Boiling point (oC)

F2

18

-188

Cl2

34

-34

Br2

70

59

I2

106

184

a)      Explain the trend in the boiling points of the halogens by describing the intermolecular forces present. (3 marks)

b)     Plot a graph of boiling point against the number of electrons. What force is directly related to number of electrons? ( 4 marks)

c)      Use your graph to predict the boiling point of astatine, the remaining member of the halogen family. ( 1 mark)

13.  The molar masses and boiling points of two carbon compounds are given in the following table. Why is there such a large difference between them in boiling point, despite their similarity in molar mass? ( Hint: Set up a page with columns as was done in the first set of Support Questions in Lesson 4.) (3 marks)

Compound

Formula

Molar mass (g/mol)

Boiling point (oC)

Ethane

C2H6

30

- 89

Methanol

CH3OH

32

65

 

  1. a) Research the space elevator concept. Consider the environment in which the cable must operate. Recommend two physical, and one chemical property that the cable should have. Justify your choices. (6 marks)

 

b) Based on what you have learned about bonding and forces in solids, which type of solid, in your opinion, is the most suitable for use in the space elevator cable? Justify your choice. (3 marks)

 

 

Subject Science
Due By (Pacific Time) 06/23/2014 08:31 am
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