chem mc help me

[匿名]

2009-02-11 8:11 pm

1. which scientist postulated that electorns can only move between certain energy levels?
a. Rutherford b. Dalton c. Einstein d. Schodinger e. bohr

2.what is the shape of a molecule of antimony(III)fluoride,SbF3?
a. linear b. trigonal planar c. trigonal pyramidal d. tetrahedral e.angular

3.whah is the shape of a molecule of krtpton tetraiodide, KrL4?
a. T-shaped b. seesaw c. trigonal bipyramidal d. square pyramidal
e. square plana

4. Predict the shape of OF3+
a. seesaw b. trigonal planar c. trigonal pyramidal d. tetrahedral
e. T-shaped

5. which compund is the best example of a molecular solidhels togrtheby London dispersion forces?
a. KI b. Na2O c. H2O d. CO2 e.NH3

6. A substance is a white powder, which melts at 660'C to give a
transparent liquid. The substance does not conduct electricity in its
solid state, but it does conduct electricity in its liquid state. How
would you classify the substance?
a.ionic b. network c. molecular d.metallic e. atomic

7. A substance is a silvery white soild, which melts at 675'C to give a
silvery liquid. The substance sonducts electricity in both its soild
and liquid states. How would you classify the substance?
a. ionic b. network c. molecular d.metallic e. atomic

回答 (1)

Uncle Michael

2009-02-12 12:50 am

✔ 最佳答案

1. e
This was proposed by Niels Henrik David Bohr, a physicist, in his atomic model. He got the Nobel Prize in 1922 for his atomic research.

2. c
Sn is a Group V element (the group of N, P, As, Sb, Bi). Think about NF3 or NCl3.

3. e
Kr is a noble gas having 8 valence electrons. It forms 4 covalent bonds with 4 I atoms, leaving 2 lone pairs of electrons. The 4 bond pairs and the 2 lone pairs locate octahedrally in shape, and the molecular shape is square planar (the two lone pairs are not considered).

4. c
O atom have 6 valence electrons, and thus the O atom in OF3+ has only 5 valence electrons only. 3 valence electrons form 3 O-F bonds and 1 lone pair of electrons is left. The 4 electron pairs are arranged tetrahedrally, and the molecular shape is trigonal pyramidal (same molecular shape as NH3).

5. d
CO2 has simple molecular structure. The non-polar CO2 molecules are held together by London dispersion forces (instantaneous dipole - induced dipole attractions)
KI and Na2O are ionic. Therefore, the opposite ions are held together by strong electrostatic forces.
H2O and NH3 have simple molecular structure. Their molecules are held together by hydrogen bonds.

6. a
Only ionic substances cannot conduct electricity in solid state, but can conduct electricity in liquid state.
Network, molecular and atomic substances cannot conduct electricity in both solid state and liquid state.
Metallic substances can conduct electricity in both solid state and liquid state.

7. d
Refer to Q.6 for the explanation.
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