[newbie!]

i have this course called "general chemistry" which texts us on everything we've learnt in our 4 years as undergrads at university.

i'd like help on the following questions:
2) Consider an ion (charge –1) containing one C, one N and one O atom.   Work out its most likely Lewis structure (briefly give reasons for your choice) and any possible resonance contributors. Use the VSEPR model to work out its shape. 
my answer
i got my marked answers back and the 1st one has been crossed wrong the other 2 have neither a tick or cross. but O-C triple bond N is written as the correct answer. why is this?

q3a) Draw two alkenes with the formula C6H11BrO which are E and Z isomers.
did this and got it correct

b) name the structures drawn above
i put 3-bromooxyhexadi-3-ene but got it marked wrong, what is the correct answer?
c) Draw two cyclic enantiomeric compounds with this molecular formula, one of which is R-configuration and one of which is S-configuration.
my answer:

which wasnt marked correct or incorrect simply had question marks drawn next to it.
i'm unsure why this is wrong?


also in the last question i needed to take logs, well reverse.
i had lnK=30.66
and i needed to get K
on my calculator (which is a sharp EL-531W) i typed ln 2nd function 30.66 giving me 3.42 however this was marked wrong and it says i;ve used the wrong calculator function.
i'm not even sure what the right value is so i can work out how to get there. anyone might know? (if i do 2nd function ln 30.66 i get 2.06 exp 13) anyone know how to get whatever the correct answer is?

[UG]

i got my marked answers back and the 1st one has been crossed wrong the other 2 have neither a tick or cross. but O-C triple bond N is written as the correct answer. why is this?

You seemed to have calculated some formal charges incorrectly, remember that the sum of all the formal charges must add up to the overall charge on the ion. For your fisrt structure on the left, the sum of all the formal charges is -3, this cannot be correct as the ion only has charge of -1.

b) name the structures drawn above
i put 3-bromooxyhexadi-3-ene but got it marked wrong, what is the correct answer?

You certainly made life difficult by drawing such a structure! Making the oxygen into an alcohol group would have made naming slightly easier I dare say, but nevertheless, the name should be (3E or 3Z)-hex-3-en-3-ylbromoniumolate according to ChemSketch

which wasnt marked correct or incorrect simply had question marks drawn next to it.
i'm unsure why this is wrong?

You need to show the stereochemistry about each bond, something like:

[UG]

also in the last question i needed to take logs, well reverse.
i had lnK=30.66
and i needed to get K

The natural log (ln) to base e is the inverse of the exponential function.
You can think of the two relationships like: ln x = y   e^y = x where e is a number stored in your calculator. I don't know exactly what your calculator looks like but usually pressing 'shift' then the 'ln' button allows you to access the base e function.
Your second answer is correct:

(if i do 2nd function ln 30.66 i get 2.06 exp 13)

[sjb]

You may also want to bear in mind that the carbon attached to the bromine is also an asymmetric centre here. Perhaps something like 3-methylpentanoyl bromide, as a relatively simple molecule with only one chiral centre?

[newbie!]

for the drawing R and S configurations i'm still a bit stuck.
even if i put in the stereochemistry i'll still have the same.
like this:

[newbie!]

also for another question i had:
ln A = 18.039
   A =  14 exp -9

which i got told i used the wrong button for.
so i retried it using the other way (which is said i got it right) (using 2nd function ln 18.039) but then i get a HUGE number 68271297.87 which seems to big to be correct?

[Borek]

also for another question i had:
ln A = 18.039
   A =  14 exp -9

which i got told i used the wrong button for.
so i retried it using the other way (which is said i got it right) (using 2nd function ln 18.039) but then i get a HUGE number 68271297.87 which seems to big to be correct?

Sorry to say that, but with this level of math you have no chances with chemistry. Logarithm and exponential function are not just keys on the calculator - these are functions, with known properties. For anyone knowing their properties it is obvious e^18.039 is a large number.

[newbie!]

cool.
so what are my units for this?