simple questions

[gomawum]

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the P680 chlorophyll A molecule of photosystem II

a. oxidize glucose
b. oxidize water
c. best absorbs light with a wavelength of 700nm
d. provides electrons that reduce NADH
e. more than one of above

- I'm not sure if Photosystem II oxidize water, and i'm ambiguous between a,d


which of following pairs gives the bond with the least ionic character?
a. Cs and F
b. O and H
c. C and C
d. C and Cl
e. C and N

- and explain me why?




which of the following has the lowest boiling point?
a. n-hexane
b. 2-methylheptane
c. 3-methylhexane
d. 2-methylpentane
e. 2-hexanol

- BP increase as MW, Intermolecular force increase, so I think it's either a or d which has the least carbons than other (e is strong since H-bond)
but what's the correct answer?


thank you

 

[2009er]

the P680 chlorophyll A molecule of photosystem II

a. oxidize glucose
b. oxidize water
c. best absorbs light with a wavelength of 700nm
d. provides electrons that reduce NADH
e. more than one of above

Photosystem II: P680 is a strong oxidizing agent and oxidizes water. water is split into 2 hydrogen atoms and an oxygen atom.

 

[joey2007]

2) C-C has the least ionic character. Ionic character is the measure between electronegativity.

3) The answer is D because branching decrease boiling pt.

 

[2009er]

which of following pairs gives the bond with the least ionic character?
a. Cs and F
b. O and H
c. C and C
d. C and Cl
e. C and N

- and explain me why?


Answer C.
because C-C bond is a nonpolar covalent bond since both the atoms have the same electronegativity.

 

[2009er]

which of the following has the lowest boiling point?
a. n-hexane
b. 2-methylheptane
c. 3-methylhexane
d. 2-methylpentane
e. 2-hexanol

Answer D. Remember that B.P. increases with increase in chain length, and decreases with increase in branching. and in the case of 2-hexanol, hydrogen bonding increases the B.P.

the following is the order of increasing B.p.:
2-methylpentane< n-hexane<3-methylhexane<2-methylheptane<2-hexanol

 

[gomawum]

but why the substitued heptane has higher bp than hexane and pentane?
does it have to do with the conformation structure?

 

[2009er]

but why the substitued heptane has higher bp than hexane and pentane?
does it have to do with the conformation structure?

the substitute heptane is composed of 8 carbons.

2-methylpentane & n-hexane
are both stuctrual isomers of C6H14, however as i mentioned earlier increas in branching causes a decrease in B.P. thus 2-methylpentane has a lower B.P. than n-hexane.

3-methylhexane = C7H16
2-methylheptane= C8H18

increasing the chain length ( in other words the back bone chain is increases) causes a increase in B.P., thus 3-methylhexane has a lower B.P than 2-methylheptane (because C6<C7<C8)

and finally in 2-hexanol there is Hydrogen bonding 😱 thus the highest B.P.

hope this helps. 😳

 

[gomawum]

very clear explanation thank you!