Hesss Law b Given the following thermochemical data AgsHNO3a

Hess\'s Law (b) Given the following thermochemical data: Ag(s)+HNO3(aq)AgNO3(aq)+½H2(g) H = 105.0 kJ H2O(l)+2AgNO3(aq) Ag2O(s)+2HNO3(aq) H= 44.8 kJ H2(g)+½O2(g) H2O(l) H =-285.8 k Use Hess\'s Law to determine H for the reaction: Ag2O(s) 1802(g) + 2Ag(s)

Solution

Lets number the reaction as 1, 2, 3, 4 from top to bottom
required reaction should be written in terms of other reaction
This is Hess Law
required reaction can be written as:
reaction 4 = -2 * (reaction 1) -1 * (reaction 2) -1 * (reaction 3)

So, Ho rxn for required reaction will be:
Ho rxn = -2 * Ho rxn(reaction 1) -1 * Ho rxn(reaction 2) -1 * Ho rxn(reaction 3)
= -2 * (105.0) -1 * (44.8) -1 * (-285.8)
= 31.0 KJ
Answer: 31.0 KJ