Consider the chemical reaction represented below. ch4 + 2o2 co2 + 2h2o + heat which of the following statements about this reaction is true? a. the reaction releases heat. b. heat is absorbed by the reaction. c. the reaction releases oxygen. d. the reaction consumes water.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

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.