Q7 Enthalpy changes can also be calculated using Hess’s Law The enthalpy of formation for pentan-1-ol is shown below 5C (s) + 6H 2(g) + O 2(g) ? C 5 H 11 OH (?) ?H = –354 kJ mol–1 Using this value, and the enthalpies of combustion of carbon and hydrogen from the
HESS’S LAW PRACTICE (1) Find the ?H for the reaction below, given the following reactions and subsequent ?H values: PCl 5 (g) ? PCl 3 (g) + Cl 2 (g) P 4
Hess' Law Practice Questions SURPASS TUTORS Answers 1 Reaction 1: C(s) + O2(g) ? CO2(g) ?H = –605 kJ Reaction
4 Find the AH for the reaction below, given the following reactions and subsequent AH values: AH = — AH = — N2(g) + 202(g) -¥ 2N02(g) + 2NH3(g)
2 Hess’s Law Extra Worksheet (6) Find the ?H for the reaction below, given the following reactions and subsequent ?H values: ½ H 2(g) + ½ Cl 2(g) ? HCl(g)
More practice- Hess's law problems Subject: SMART Board Interactive Whiteboard Notes Keywords: Notes,Whiteboard,Whiteboard Page,Notebook software,Notebook,PDF,SMART,SMART Technologies ULC,SMART Board Interactive Whiteboard Created Date: 7/13/2013 5:37:00 PM
Summary of Hess's Law • A reaction and its reverse have equal magnitude, opposite sign ΔH values If A → B has ΔH = 100 kJ, then B → A has ΔH = –100 kJ