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26 Nov 2019

The electron affinity of an element is positive if energy isabsorbed during the process of accepting an electron and negativeif energy is released during the process. Classify the followingreactions according to their electron affinity values using theelectron configuration of the atom or ion undergoing the additionof an electron.

Ne 1s2 2s2 2p6
Cl 1s2 2s2 2p6 3s2 3p5
Na 1s2 2s2 2p6 3s1
Mg 1s2 2s2 2p6 3s2
Br- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6

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Related questions

1) What are the possible orbitals for n=3?

  1. s, p, d
  2. s, p, d, f
  3. s
  4. s, p

 

2) What value of ℓ is represented by a d orbital?  

  1. 1
  2. 2  
  3. 0
  4. 3

 

3) How many orbitals are contained in the third principal level (n=3) of a given atom?

  1. 9
  2. 3
  3. 18
  4. 7
  5. 5

 

4) Which of the following statements is TRUE?

  1. The principal quantum number (n) describes the shape of an orbital.
  2. The angular momentum quantum number (ℓ) describes the size and energy associated with an orbital
  3. The magnetic quantum number (mℓ) describes the orientation of the orbital.
  4. An orbital is a path that an electron follows during its movement in an atom
  5. All of the above are true

 

5) Which of the following transitions represents the emission of a photon with the largest energy?

  1. n=2 to n=1
  2. n=3 to n=1
  3. n=6 to n=4
  4. n=1 to n=4
  5. n=2 to n=4

 

6) Choose the transition (in a hydrogen atom) below that represents the absorption of the shortest wavelength photon.

  1. n=1 to n=2
  2. n=2 to n=3
  3. n=4 to n=5
  4. n=6 to n=3
  5. n=3 to n=1

 

7) Each of the following sets of quantum numbers is supposed to specify an orbital. Choose the one set of quantum numbers that does not contain an error.

  1. n=2, ℓ =2, mℓ= +1
  2. n=2, ℓ=2, mℓ= 0
  3. n=3, ℓ=2, mℓ = -3
  4. n=4, ℓ=3, mℓ= -2
  5. n=4, ℓ=2, mℓ= +4

 

8) The element that corresponds to the electron configuration 1s2 2s2 2p6 3s2 3p6 4s1 3d5 is:

  1. titanium
  2. vanadium
  3. chromium
  4. manganese
  5. iron

 

9) Give the ground-state electron configuration for I.

  1. [Kr] 5s2 4d10 5p6
  2. [Kr] 5s2 4d10 5p5
  3. [Kr] 4d10 5p6
  4. [Kr] 5s2 5p6
  5. [Kr] 5s2 5d10 5p6

 

10) Place the following elements in order of increasing atomic radius

            P                      Ba                    Cl

  1. Ba < P < Cl
  2. P < Cl < Ba
  3. Cl < P < Ba
  4. Cl < Ba < P
  5. Ba < Cl < P

 


Practice problems for exam 2 ______________

Useful Information:

h=6.626×10-34J·s.; c=3.0×108 m/sec; E=h ; E= hc ,  = h/mv; 1J = 1 kg-m2/s2 

mass of electron = 9.11 × 10-28 g, E= q + w ; 1 cal = 4.184 Joules Please Show all Work

1. Which of the following substances have standard heats of formation that are equal to zero by definition (circle your answers): H2(g), H(g), O3(g), H2O(s), H2O(l), Hg(l), Hg(s), Hg(g).

2. Limestone stalactites are formed in the reaction: Ca2+(aq) + HCO3-(aq) ïƒ CaCO3(s) + CO2(g) +

H2O(l)
If one mole of CaCO3 is produced at 298 K under one atmosphere of pressure, the reaction performs 590 calories of expansion work, pushing back the atmosphere as CO2 is formed. At the same time, 9310 calories of heat are absorbed from the environment. What is E in Kcal/mole for CaCO3.

3. What is the minimum wavelength of light in Å (1 Å = 10-8 cm) needed to provide enough energy per quantum to rupture the chemical bond in hydrogen iodide (HI). The bond dissociation energy of HI is 71.4 Kcal/mole.

1

4. Sketch the shape and orientation of the following types of orbitals: s, px, dxy, dz2, dx2-y2

5. Give the values of (n) , (l) and (ml) for each orbital in the 4p subshell.

6. Write the complete electron configuration for the following: Ti 2+_____________________________________ Cr_______________________________________

N______________________________________

7. Calculate the standard enthalpy of formation (  Ho) for diamond from graphite [i.e. C (graphite) ïƒ C (diamond)] given that:

C (graphite) + O2 ïƒ CO2 (g) (  Ho = -393.5 KJ/mole) C (diamond)] + O2 ïƒ CO2 (g) (  Ho = -395.4 KJ/mole)

If 1.0g of graphite is converted to diamond, what is the energy change? Is this an endothermic or exothermic reaction?

2

8. An 160 pound astronaut on his way to Mars is buzzing along at 10,000 miles per hour. (a) Express his weight in grams (one pound = 454 grams) so that you can calculate the astronaut’s wavelength (1mile/hour = 44.7 cm/sec)

(b) Suppose the astronaut detects outside his spacecraft a proton (m=1.7 x 10-24 g) from a “solar wind” moving at exactly the spacecraft velocity. What is the proton wavelength is in Å (1 Å = 10-8 cm.

9. What is the maximum number of electrons that can occupy each of the following subshells? a) 3d_________________ b) 1s____________________ c) 2p ____________________

10. Identify the element represented by the following electronic configuration.

a) [Ne] 3s2____________________

b) What is the electron configuration for the first excited state of this atom.______________

11. Determine the number of valence electrons for each element.
(a) Br___________ (b) Na _________ (c) Sn __________

3

12. 175 g of Fe at 15.0oC is mixed with 225 g of H2O at 95.0oC. What is the final temperature of the mixture? The specific heats of iron= 0.448 J/g oC and water = 4.184 J/g oC). (keep in mind the following: heat gained + heat lost = 0 and q=mass x heat capacity x T)

13. (5 pts) Calculate values of ΔHrxn for the following reactions: CS2(g) + 3O2(g)  CO2(g) + 2SO2(g)

The heat of formation for the following substances is given in kJ/mol:

CS2 CO2 SO2 117.4 -393.51 -296.83

14. (6 pts) Use the electron configuration of Li and Be and determine which element has the greatest second ionization energy. Defend your answer.

4

15. Mark beside each of the following processes either “exo” or “endo” according to whether you think the process will release heat or absorb heat.

a. Ca(g) ïƒ Ca(g)+2 + 2e-
b. I(g)+1e-ïƒ I(g)-1
c. Ca(g)+2 + S(g)-2 ïƒ CaS(s) d. I2(g)ïƒ 2I(g)

( ) ( ) ( ) ( )

16. (6 pts) In each of the following pairs, which of the two species is larger?
a) O-2 or Na+ b) Ti+4 or Ti+2 c) B or C d) N or N-3

17. Write down the Lewis dot structure for the following (a) N_______________ (b) Ne________________

18. THE BORN HABER CYCLE: I may have a problem on the Born Haber cycle. Please check my lecture notes to see how to set up the process and then calculate the lattice energy from the various thermodynamic quantities such as in the NaCl example below;

 H  f NaCl = -411KJ

Na(s)  Na(g)  H =108KJ
1⁄2 Cl2  Cl(g)  H = 122KJ Ionization Energy of Na  H = 496 KJ Electron affinity of Cl  H = -349KJ

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