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When 1 mole A reacts with ½ mole of B2 (A + ½B2 = AB), 100 Kcal heat is liberated and when 1 mole of  A reacts with 2 mole of B2( A + 2B2= AB4), 200 Kcal heat is liberated . When 1 mole of A is completely reacted with excess, of B2 to form AB as well as AB4, 140 Kcal heat is liberated calculate the mole of B2 used.

A + 1/2B2 --> AB   delta H = 100kcal
A + 2B2 ---> AB4    delta H = 200kcal
Add above two equations
2A + 2.5 B₂ ---> AB + AB₄    delta H = (100  + 200)kcal =300kcal
For one mole of A
A + 5/4 B₂ ---> 1/2 AB + 1/2 AB₄    delta H = 300/2  kcal

Hence number moles of B₂ used here =  140kcal* 5/4 moles B₂/ 150 kcal = 1.16 moles B₂