5 Steps to a 5 AP Chemistry

d. This part requires Graham’s law: r 1 /r 2 =(M 2 /M 1 )1/2

If we let “1” refer to hexane, and “2” refer to the unknown vapor, then: r 1 =(1/2)r 2 , and

M 1 =86.17 g/mol. When these values are entered into the equation:

Canceling and then squaring both sides gives:

(1/2)^2 =(1/4)=M 2 /86.17 g/mol

M 2 =(1/4)(86.17 g/mol) =21.54 g/mol

Give yourself 2 points for the correct setup and the correct answer. It is not necessary

to show all the intermediate steps. Give yourself 1 point if you make a mistake.

e. You may need to redraw one or more of your answers to match the answers shown

below. Give yourself 1 point for each correct answer, with a 2-point maximum. There

are no bonus points for additional answers.

These compounds are 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane and

2,3-dimethylbutane, respectively. These four, along with the original n-hexane, are the

only isomers. If you think you have another isomer, you have simply redrawn one of

these. Try naming your answer and see if it matches one of these names.

Total your points. The maximum is 10 points. Subtract one point if all your answers

do not have the correct number of significant figures.

 Rapid Review

 Organic chemistry is the chemistry of carbon and its compounds.

 Hydrocarbons are organic compounds of just carbon and hydrogen atoms.

 Alkanes are hydrocarbons in which there are only single bonds.

 Alkanes are named in a very systematic way. Review the rules for naming alkanes.

 Isomers are compounds that have the same molecular formulas but different structural

formulas. Review the writing of the various structural isomers of alkanes. Make sure that

each carbon atom has four bonds.

 A functional group is a group of atoms that is the reactive part of the molecule. Review

the general functional groups.

 Macromolecules are large molecules that may have molecular masses in the millions.

Macromolecules are generally composed of repeating units called monomers.

H

HC C CCC CC C CCHH

HHCH

H

HH

HH

H

C HH H

CCC CHHC

HHCH

H

H H

CCCH

H HH

H

H H C

HH

HHHCH

H

HHHH HH

H

CHH

HHHH HH HHH

12

(^2) 86 17
2
2

()^12

=()

r

r

M /g/mol.

Organic Chemistry  277