4) An unlabeled laboratory solution is found to contain an OH ion concentration of 6.7 x 10-6 M. What is the H+ concentration in the solution?
A) 6.7 x 10-20 M
B) 6.7 x 108 M.
C) 1.49 x 10-20 M
D) 1.49 x 10-9 M

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".

5 structural isomers

the isomers are:

n-exane :   ch3ch2ch2ch2ch2ch3

2-methylpentane :   ch3ch(ch3)ch2ch2ch3

3-methylpentane :   ch3ch2ch(ch3)ch2ch3

2,3-dimethylbutane :   (ch3)2chch(ch3)2

2,2-dimethylbutane :   (ch3)3cch2ch3