The standard heats of combustion (δh∘) per mole of 1,3-butadiene, c4h6(g); butane, c4h10(g); and h2(g) are −2540.2,−2877.6, and −285.8kj, respectively. use these data to calculate the heat of hydrogenation of 1,3-butadiene to butane. c4h6(g)+2h2(g)→c4h10(g)

solution:

Hydration is the addition of water; hydrogenation is the addition of hydrogen.  

desire rxn: _C4H6(g) + 2 H2(g)> C4H10(g)___dHhy = ??  

knowns:  

C4H6 + 11/2 O2 > 4CO2 + 3H2OdHox = -2540.2 kJ/mole  

4CO2 + 5H2O > C4H10 + 13/2 O2___-dHox = 2877.6 kJ/mole  

2(1/2 O2 + H2 > H2O)2*dHox = 2(-285.8 kJ/mole)  

Basic mathematics is a prerequisite to chemistry – I just try to help you with the methodology of solving the problem

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.