YOUR NAME                                                                                 

 

Chemistry 1201 Lecture Section 2 & 3

HOMEWORK #4 due on Thursday April 18 (sect. 2) and on Friday, April 19 (sect. 3), 2002

STAPLE your work to this answer sheet and hand in to me in class.

The maximum score attainable is 25.

 

PART I - Provide answers by filling in the blanks.

Suggestion: Draw Lewis structures for ALL species on a scrap sheet of paper

(I do not need to collect it) BEFORE you attempt to answer the questions.

 

Consider the following species when answering the next 5 questions (1 mark each) .

 

(i) PCl3           (ii) CH 2Cl2            (iii) HCN                         (iv) C2H4            (v) NH 3

 

Q1:  In the Lewis structure(s) of                                  the central atom has one lone pair of electrons. There may be more than one structure that qualifies!

 

Q2: The Lewis structure with the largest total number of lone pairs of electrons is            .

 

Q3: The Lewis structures of                             have to have multiple bonds in order to satisfy octet on all atoms other than hydrogen. There may be more than one molecule that qualifies!

 

Q4: The central atom is the most electronegative atom in                                . There may be more than one molecule that qualifies!

 

Q5: Can any of the Lewis structures for the above molecules be drawn with non-zero formal charge(s) on any of the atoms?
Yes                         No                   

 

Consider the following species when answering the next 4 questions (1 mark each) .

 

i) NO2 -        (ii) NO3 -           (iii) CO3 2-                (iv) SO42 -             (v)BrO3-

 

Q6:  The central atoms in                                  cannot expand octet. There may be more than one ion that qualifies!

 

Q7: The Lewis structure of                   cannot be drawn without a non-zero formal charge on the central atom.

 

Q8: Lewis structures of                                    can be drawn with and without expanding the octet on the central atom. There may be more than one ion that qualifies!

 

Q9: Can any of the Lewis structures be drawn with all formal charges being zero?

Yes                                           No                  

 

PART II - Provide solutions on a separate piece of paper.

 

Q10 (5 marks): Draw ALL Lewis structures of the sulfite anion, SO32-, ("ALL" means regardless whether the octet rule is adhered to or not), and point to the one(s) which are the best (MAJOR). Remember that in order for a Lewis structure to be complete, you must include all electrons, formal charges, and the overall charge of the ion.

 

 

Q11 (5 marks): Estimate the enthalpy of reaction, Delta Hrxn , in kJ/mol, for the reaction:

 

            C6H12O6(s) --> 6 CO2(g) + 2 CH3COOH

 

Use the structural formula of alpha-glucose, C6H12O6, shown on page 996 in your textbook.

 

Answer:

 

 

 

Now, recalculate your results to make sure you haven't made a calculational error J

 

PART III - Complete the following table:

Q12 (6 marks):

 

Formula

Systematic Name

(NH4)2Cr2O7

 

Ca(HCO3)2

 

Magnesium permanganate

 

Potassium phosphate

FeCl3

 

 

Copper(II) sulfate