CHEM 1040 Study Guide - Final Guide: Lattice Energy, Bond-Dissociation Energy, Hydrazine

• School: University of Guelph
• Department: Chemistry
• Course: CHEM 1040
• Professor: wenoika

Document Summary

Problems: given the following, determine a value for the n n bond enthalpy in hydrazine, n2h4(g) (a rocket fuel which is discussed on p. 251 (p. 253) in the text). Heat of formation of liquid hydrazine is +51 kj mol 1. Heat of vaporisation of liquid hydrazine is +48 kj mol 1. Bond energies: n n is +942 kj h h is +432 kj n h is +386 kj. Solution: n2(g) + 2h2(g) n2h4(l); h f = +51 kj. N2(g) + 2h2(g) n2h4(g); h rxn = +99 kj. Now that all of the above is in the gas phase, we can use bond energies: H rxn = +99 kj = be(n ) + 2be(h h) be(n n) 4be(n h) +99 kj = 942 kj + 2(432 kj) be(n n) 4(386 kj) Be(n n) = 163 kj: given the following (kj) data, estimate a value for the cs bond enthalpy in cs2(g).