How many oxygen molecules are in a flask that contains 1.43 grams of oxygen?

(1.43 g O2) / (31.99886 g O2/mol) x (6.022 x 10^23 molecules/mol) = 2.69 × 10^22 molecules O2

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante

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.