Question #0d7fc

1 Answer
Ernest Z.
Nov 20, 2016

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

Explanation:

"C(s) + 2F"_2 "(g) → CF"_4 "(g)"; Δ_text(rxn)H = "-933 kJ/mol CF"_4

(a) Using 2 mol of "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 "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 "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

"CF"_4"(g)" → "C(s) + 2F"_2"(g)"; Δ_text(rxn)H = "+933 kJ/mol CF"_4

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