Calculate the number of molecules in 7 moles of oxygen

4.21

Explanation:

use Avogadro's number

6.023 x 10^23

multiply this by 7 because you want to find 7 moles :

6.023 x 10^23 x 7 = 4.21

they both have a y in them

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.