Name:______Student No.______

Professor Skeels

The following is the First Examination for Chemistry and the Environment CHEM106/ENVS106, Fall Semester 2004.

Exam Instructions

  1. All notebooks, coats, knapsacks, etc. must be stored underneath your chair before the exam begins.
  1. Supporting work and calculations must be shown in order to receive full credit for a question.
  1. Work must be legible to be graded. Unreadable work will not receive credit.
  1. If you have a questions, raise your hand and ask the instructor. Some questions cannot be answered.
  1. Clearly indicate your choices.
  1. Work MUST be in pen.
  1. Honor statement must be signed in order for the exam to be graded.
  1. Good Luck!!

Honor Statement.

By signing my name on the line below, I guarantee that all of the work I am submitting in this exam is my own work; I have not copied another student’s work nor have I unethically obtained information about this exam from others. Additionally, by my signature I also guarantee that I will not discuss the exam with students whom have not taken the exam.

I understand that even if I do sign this honor code, if any of my work is found to violate the terms stated above I will be subject to scrutiny of the University Honor Committee.

______

(Student Signature)

  1. Write balanced equations to represent these reactions

a)Nitrogen gas (N2) reacting with oxygen gas (O2) to give nitric oxude (NO)

Answer:

N2 + O2 = 2NO

b)Sulfur (S) reacting with oxygen gas (O2) to form sulfur trioxide (SO3)

Answer:

2S + 3O2 = 2SO3

  1. Balance and indicate complete or incomplete combustion for the following:

a)C3H8 + O 2 = CO + H2O

Answer:

2C3H8 + 7 O 2 = 6 CO + 8 H2O (Incomplete combustion)

Note: smokeformation is another incomplete combustion, but instead of carbon monoxide, Carbon (C) is the major product

b)C8H18 + O 2 = CO2 + H2O

Answer:

2 C8H18 + 25 O 2 = 16 CO2 + 18 H2O (Complete combustion)

  1. Lewis structures:

A) SH2 B) CF4 C) OClF D) NF3 E) AsH3

Answers:

A)H-S-H

B)NOTE – I don’t have ChemDraw so I can’t draw these. I will describe them …

One carbon atom in center surrounded by four covalently bound (sharing electron pair) Fluorine atoms. Each fluorine atom has three pairs of NON-bonding electrons.

C)Cl-O-F

Electrons must be placed so that Cl has three pairs of nonbonding electrons, as does F. Oxygen has only two pairs of non-bonding electrons

..

D)F-N-F

|

F

3 non bonding pairs of electrons must be included around each F.

..

E)H-As--H

|

H

  1. Draw two isotopes of any element:

Answer: An isotope has same number of protons, but differs in number of neutrons

Ahh … lets use chlorine …

17 35Cl and 17 36Cl

  1. What are some of the health effects of the four EPA listed Air Pollutants.

Answer: see class notes.

  1. Ozone (O3) and oxygen (O2) are _(B)______

a)isotopes

b)Allotropes

c)Elements

d)Atoms

e)Covalent bonds

  1. Photons are ______

Answer: particle w/no mass – packets or ‘quanta’ of energy

  1. What is a free –radical ?