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These are the ones I can't get

I also don't get why they put the questions up before they go over the material

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1.

A student drew an incorrect Lewis structure for C2Cl4 as show below:

c2cl4x.jpg

Which of the following statements are true for the corrections that need to be made to the students drawing ?

a) Three chlorine atoms should be bonded to the same carbon atom

:) The carbon atom should not have a lone pair of electrons

c) Two chlorine atoms should exceed an octet of electrons

d) There should be a C=C bond

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2.

Which of the following compounds can exist as cis and trans isomers ?

a) CHCl=CHCl

B) CH2=CH-CHCl2

c) ClBrCHCl

d) CBrH=CH-CH2Cl

e) 3-hexene

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3.

Using average bond energy values estimate ΔH for the following gas phase reaction.

C3H8 + 5O2 → 3CO2 + 4H2O

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4.

Which of the following compounds present exceptions to the octet rule ?

a) NH4+

B) ClO4-

c) PO4-3

d) ClF3

e) SO3-2

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5.

Choose those statements that are true about the two best resonance structures of HNNN.

a) There are a total of sixteen valence electrons in each of these resonance structures.

B) The best resonance structure has a formal charge of zero on all of the atoms

c) The best resonance structure has a formal charge of -1 on one of the nitrogen atoms

d) Only one resonance structure has nonbonded electron paris

e) The two best resonance structures have the same number of bonding electrons

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6.

lewis1.gif

Choose the statements that are true about the proposed Lewis structure shown above for the molecule [HCNH]+

Base your answers on the struture as drawn here.

a) This is a proper Lewis structure in that the number of valence electrons shown is correct

B) Neither C or N have an octet of electrons

c) In this Lewis structure the formal positive charge is on the carbon atom

d) A much more correct Lewis structre can be drawn for the molecule [HCNH]+

You must enter the letters you choose in one continuous alphabetical group with no spaces between the letters.

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Thanks for any help :wub:

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1. d, because Cl cant form a = bond with C, so inorder to balance this, the lone pair on the C has to move over to the Cl and the = bond should be C=C

2.

a) CHCl=CHCl <-- will be same thing on each side... i guess it can form cis/trans with the Cl's and with the hydrogens on same or oppisite sides...

:wub: CH2=CH-CHCl2 <-- only one side with a longer bond...

c) ClBrCHCl <-- no double bond...

d) CBrH=CH-CH2Cl <-- if you consider Br a longer chain then this can be correct.

e) 3-hexene <-- triple bond = linear no cis/trans

no idea about the rest...

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1. d, because Cl cant form a = bond with C, so inorder to balance this, the lone pair on the C has to move over to the Cl and the = bond should be C=C

2.

a) CHCl=CHCl <-- will be same thing on each side... i guess it can form cis/trans with the Cl's and with the hydrogens on same or oppisite sides...

:wub: CH2=CH-CHCl2 <-- only one side with a longer bond...

c) ClBrCHCl <-- no double bond...

d) CBrH=CH-CH2Cl <-- if you consider Br a longer chain then this can be correct.

e) 3-hexene <-- triple bond = linear no cis/trans

no idea about the rest...

okay thanks

>_< its electronic and I have 1 try left

#1- d was wrong x_x

#2- the cis/trans thing, i got it.. A,D,E were right

thanks

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Do they have multiple correct answers (It seems like it)?

#1 B and D Are correct

#2 A, D, and E are correct

#3 The bond energies should be given. Such as C-H, O=O bond etc. in values. (They are generally in KJ/Mol) Then you take reactant bond energy - product bond energy (yes i know its an odd react-prod). It should be negative. That will be your Delta H

Ex. CH4 + 2O2-> CO2 + 2H20

C-H Bond Energy 413kj/mol

O=O 498kj/mol

(Other bond energies will be given)

So 4*413 + 2*498 - (Product bond energy)

#4 B, C, and D

#5 Gay, just draw them and make a relation.

#6 A (IDK about D (but doubt it). It looks fine (based on what HCN looks like). I've never seen that chemical before and don't even know how to name it.)

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Do they have multiple correct answers (It seems like it)?

#1 B and D Are correct

#2 A, D, and E are correct

#3 The bond energies should be given. Such as C-H, O=O bond etc. in values. (They are generally in KJ/Mol) Then you take reactant bond energy - product bond energy (yes i know its an odd react-prod). It should be negative. That will be your Delta H

Ex. CH4 + 2O2-> CO2 + 2H20

C-H Bond Energy 413kj/mol

O=O 498kj/mol

(Other bond energies will be given)

So 4*413 + 2*498 - (Product bond energy)

#4 B, C, and D

#5 Gay, just draw them and make a relation.

#6 A (IDK about D (but doubt it). It looks fine (based on what HCN looks like). I've never seen that chemical before and don't even know how to name it.)

you're right about 6.

btw HCN = hydrogen cyanide

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