Answer
More substituted alkene is more stable than less substituted therefore has less amount of heat of hydrogenation.
Work Step by Step
Heat of hydrogenation is the heat give off from the reaction when alkene reacts with %H_2$, the more heat is given off, the more likely the reaction to occur and the more unstable the alkene is. Based on Table 7.1, heat of hydrogenation of 2,3-dimethyl-but-1-ene is 117kJ and 2,3-dimethylbut-2-ene is 111kJ. The difference in energy is 117-111=6kJ; 2,3-dimethyl-but-1-ene has higher heat of hydrogenation than the other, therefore it is less stable.
=>More substituted alkene is more stable than less substituted
