In the reaction, 2H2(g) + O2(g) which the reactants appear is:
2H2O(1), the phase of matter in
a) solid.
b) liquid.
c) gas.
d) plasma.

b liquid

Explanation:

2H

2

(g)+O

2

(g)⟶2H

2

O(l) is the correction reaction as during formation of water both hydrogen and oxygen are in gaseous form and produces water in liquid form.

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.