ACS Chem question

[dental13]

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The question is following

The O-Si-O bond angles in SiO2(quartz) are closest to
a. 180
b. 120
c. 110
d. 100

I thought this was an easy question and went for choice a. 180, but ACS answer sheet is telling me it's C.

So I drew the lewis structure and all I can draw is linear structure. Am I missing something here?

Another question is...
Resonance structures describe molecules that have
a. hybrid orbitals
b. rapid equilibria
c. resonating electrons
d. multiple electron-dot formulas

I thought answer was b, but the answer is d.
Since ACS only gives me answers without explanation, I need you guys 🙂

 

[wired202808]

The question is following

The O-Si-O bond angles in SiO2(quartz) are closest to
a. 180
b. 120
c. 110
d. 100

I thought this was an easy question and went for choice a. 180, but ACS answer sheet is telling me it's C.

So I drew the lewis structure and all I can draw is linear structure. Am I missing something here?

The answer is C because SiO2 is a network solid (quartz) just like (diamond and graphite) so when you draw it out, its not quite linear at 120, its actually slightly bent and should be at 110. Hope this helps. This is one of those exceptions you have to remember.

 

[wired202808]

Another question is...
Resonance structures describe molecules that have
a. hybrid orbitals
b. rapid equilibria
c. resonating electrons
d. multiple electron-dot formulas

I thought answer was b, but the answer is d.
Since ACS only gives me answers without explanation, I need you guys 🙂

I'm not sure what rapid equilbria means but A and C are also absurd; however D makes sense since resonance between Oxygens would produce oxygens with different arrangements of electron dot structures depending on whether the O is +, -, or neutral.

 

[dantemac]

Yeah, SiO2 is bent like water! The bond angle would not be 180 deg.

Also, resonance structures show where in the molecule electrons move back and forth. Remember that no one resonance structure is the correct one, the electrons are always moving around. Hence the answer.

 

[dental13]

Yeah, SiO2 is bent like water! The bond angle would not be 180 deg.

Also, resonance structures show where in the molecule electrons move back and forth. Remember that no one resonance structure is the correct one, the electrons are always moving around. Hence the answer.

I am not seeing why SiO2 is bent molecule, SiO2 has 16 valence electrons and if you apply VESPER theory, Si will double bond to both Oxygen and form linear. in order to be bent, Si must have two sigma bonds and two paired electrons... but SiO2 does not have that. I guess I will memorize it as exception then.

 

[ScratchMan]

I am not seeing why SiO2 is bent molecule, SiO2 has 16 valence electrons and if you apply VESPER theory, Si will double bond to both Oxygen and form linear. in order to be bent, Si must have two sigma bonds and two paired electrons... but SiO2 does not have that. I guess I will memorize it as exception then.

http://answers.yahoo.com/question/index?qid=20090417191917AAe4pwi
Its explanation makes sense.... 🙂🙂

 

[dantemac]

Yeah that answer makes better sense. 4 e- domains = Tetrahedral.