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Kit Kit 發問於 科學及數學化學 · 10 年前

Chem MC 幾條 (20分)

1. Which of the following gives the correct order of electronegativities?

A. F>Cl>O>H

B. Cl>O>N>S

C. O>S>H>Si

D. Cl>N>O>F

2. Which of the following elements has the lowest electronegativity?

A. Li

B. K

C. Be

D. Mg

3. Which of the following covalent bonds is the most polar one?

A. H-Cl

B. S-F

C. Si-O

D. P-Br

4. Which of the following molecules are non-polar?

(1) CS2

(2) H2S

(3) SF6

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1) , (2) and (3)

5. Which of the following is the correct description for a PF5 molecule?

A. It is a polar molecule with five polar bonds.

B. It is a polar molecule without dipole moment.

C. It is a symmetrical, non-polar molecule.

D. It is an unsymmetrical, non-polar molecule.

6. Which of the following molecule(s) is / are polar?

(1) NF3

(2) BCl3

(3) BeCl2

A. (1) only

B. (2) only

C. (1) and (3) only

D. (2) and (3) only

Thx a lot...

2 個解答

  • 10 年前

    1) C.

    By looking at the periodic table (with Pauling scale) you will find out why.

    2) B.


    By looking at the table mentioned above, you will find that the elements are situated much leftward and downward usually have lower electronegativity while that are situated rightward and upward usually have higher electronegativity.

    3) C

    The higher the difference of electronegativity, the higher the polarity.

    ( You had better check whether I am right cos I can't remember this well)

    Just doing some substraction

    4) B.

    Carbon disulphide: Linear shape, like CO2

    the dipole moment move oppositely.

    vector sum = 0. Non-Polar!

    Hydrogen Sulphide: V-shaped, like H2O

    the dipole moment gives the vector sum of non-zero. POLAR!

    Sulphur Hexaflrouride: Octahedral

    Vertical dipole movement = 0

    Horizontal dipole movement = 0

    No vector sum. Non-polor!

    5) C

    Trigonal Bipyramidal. The explanation of polarity has been explained above.

    6) A

    Look at their shape can explain the polarities of the compounds.

    Sorry for my poor English and knowledge of Chemsitry

    For question 4, I answered you accroding to my textbook.

    Others from my own knowledge!!!

    Hope it helps you! Good luck!

    If any problems arised, ask me!

    If others find some mistakes, tell me!

    資料來源: My Knowledge, My textbook ( Polarity), Wiki (Pauling scale)
  • 10 年前

    1.C (F>O>N>Cl>S>H>Si)

    2.B (the left hand corner)

    3. C (the difference in Electronegativity is the highest in C)

    4.B (CS2 is linear and SF6 is octahedral)

    (H2S is V-shaped and hence it is polar)

    5.C PF5 is non polar molecule since it is trigonal Bipyramidal

    6.A(NF3 is trigonal pyramidal BCl3 is trigonal planer BeCl2 is trigonal Bipyramidal)

    資料來源: me