CHEMISTRY

Exercise 7.55: Problems by Topic – Orbitals and Quantum Numbers

Part A

Which electron is, on average, closer to the nucleus: an electron in a 2s orbital or an electron in a 3s orbital?

ANSWER:

[removed]an electron in a 2s orbital
[removed]an electron in a 3s orbital

Correct

Exercise 7.41: Problems by Topic – Electromagnetic Radiation

Calculate the frequency of each of the following wave lengths of electromagnetic radiation.

Part A

488.0 nm (wavelength of argon laser)

Express your answer using four significant figures.

ANSWER:

Part B

503.0 nm (wavelength of maximum solar radiation)

Express your answer using four significant figures.

ANSWER:

Part C

337.1 nm (wavelength of nitrogen laser)

Express your answer using four significant figures.

ANSWER:

 

hemistry 113 Practice Exam 4 Spring 2016                                                                                           

Directions on actual Exam: The exam consists of 2 sections (Chemical Bonding and Geometry and IMFs. Each multiple choice question is worth 4.33 points. You are allowed to use a scientific (nonprogrammable) calculator, periodic table, and VSEPR Theory Table.

 

Useful information:

ΔH°rxn  =  Σn×D(bonds broken) – Σn×D(bonds formed)

where Σn represents the sum of the moles of a particular type of bond

D represents bond energy per mole of bond

Chemical Bonding and Geometry

1. The Lewis dot symbol for the calcium ion is
   

A)

2+
  B) ¾Ca¾
   

C)

2+
  D) Ca2+
  E) Ca

 

2. The electron dot structure for AsCl3 molecule shows

 

  A) a total of 84 electron dots
  B) three single bonds and 10 lone pairs
  C) two single bonds, one double bond, and 9 lone pairs
  D) one single bond, two double bonds, and 8 lone pairs
  E) three single bonds and one lone pair

 

 

 

3. The correct Lewis structure for CO2 is: C

 

A)

 

 

B)

 

 

C)

 

 

O

D)

4. Which of the following Lewis structures is incorrect?
   

A)

  B)
   

C)

   

D)

  E)

 

5. How many covalent bonds will be formed by bromine in BrO3 for the dot structure that expands the octet to minimize formal charge and places negative formal charges on only the most electronegative atom(s). The Pauling electronegativity values are:

Br = 2.8; O = 3.5

 

  A) 3
  B) 4
  C) 5
  D) 6
  E) 7

 

 

6. Estimate the enthalpy change for the reaction 2CO + O2 ® 2CO2 given the following bond energies.

BE(CºO) = 1074 kJ/mol

BE(O=O) = 499 kJ/mol

BE(C=O) = 802 kJ/mol

 

  A) +2380 kJ/mol
  B) +744 kJ/mol
  C) +1949 kJ/mol
  D) –561 kJ/mol
  E) –744 kJ/mol

 

7. Give the number of lone pairs around the central atom and the molecular shape of the ion ClO3.

 

  A) 0 lone pairs, trigonal
  B) 1 lone pair, bent
  C) 1 lone pair, trigonal pyramidal
  D) 2 lone pairs, T-shaped
  E) 2 lone pairs, trigonal

 

8. Which of the following substances is/are bent?

(i)  H2S      (ii).  CO2      (iii)  ClNO     (iv)  NH2    (v)  O3

 

  A) only (iii)
  B) only (i) and (v)
  C) only (i), (iii), and (v)
  D) all are bent except for (iv)
  E) all are bent except for (ii)

 

 

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