Given the following reactions, what is the overall enthalpy change for the following reaction? NH_3(g) + HCl(g) right arrow NH_4Cl(s) .

-176.0 kJ/mol

Explanation:

Let's consider the following balanced reaction.

NH₃(g) + HCl(g) → NH₄Cl(s)

We can calculate the standard enthalpy change for the reaction (ΔH°rxn) using the following expression.

ΔH°rxn = 1 mol × ΔH°f(NH₄Cl(s)) - 1 mol × ΔH°f(NH₃(g)) - 1 mol × ΔH°f(HCl(g))

ΔH°rxn = 1 mol × (-314.4 kJ/mol) - 1 mol × (-46.1 kJ/mol) - 1 mol × (-92.3 kJ/mol)

ΔH°rxn = -176.0 kJ/mol

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.