# Question 0d7fc

Nov 20, 2016

Δ_"rxn"H = "-1900 kJ, -930 kJ, -1900 kJ, and +933 kJ/mol CF"_4, respectively.

#### Explanation:

${\text{C(s) + 2F"_2 "(g) → CF"_4 "(g)"; Δ_text(rxn)H = "-933 kJ/mol CF}}_{4}$

(a) Using 2 mol of $\text{C}$

Δ_text(rxn)H = 2.0 color(red)(cancel(color(black)("mol C"))) × (1 color(red)(cancel(color(black)("mol CF"_4))))/(1 color(red)(cancel(color(black)("mol C")))) × "-933 kJ"/(1 color(red)(cancel(color(black)("mol CF"_4)))) = "-1900 kJ"

(b) Using 2 mol of ${\text{F}}_{2}$

Δ_text(rxn)H = 2.0color(red)(cancel(color(black)("mol F"_2))) × (1 color(red)(cancel(color(black)("mol CF"_4))))/(2 color(red)(cancel(color(black)("mol F"_2)))) × "-933 kJ"/(1 color(red)(cancel(color(black)("mol CF"_4)))) = "-930 kJ"

(c) Using 2 mol of ${\text{CF}}_{4}$

Δ_text(rxn)H = 2.0 color(red)(cancel(color(black)("mol CF"_4))) × "-933 kJ"/(1 color(red)(cancel(color(black)("mol CF"_4)))) = "-1900 kJ"#

(d) Reversing the reaction

${\text{CF"_4"(g)" → "C(s) + 2F"_2"(g)"; Δ_text(rxn)H = "+933 kJ/mol CF}}_{4}$