Q1: The heat evolved in the combustion of benzene is represented by the equation:
    C₆H₆ + 7.5 O₂ = 6CO₂ + 3H₂O, ΔH = 3264.6 kJ/kg. mole
The heat energy change, when 39 gm of C₆H₆ is burnt in an open container, will be __________ kJ/kgmole.

ANS:C - -1632.3

To find the heat energy change when 39 g of 𝐶6𝐻6C6​H6​ is burnt, we'll first calculate the number of moles of 𝐶6𝐻6C6​H6​, then use the given enthalpy change per mole to find the total heat energy change.

1. Calculate the moles of 𝐶6𝐻6C6​H6​: Molar mass of 𝐶6𝐻6=(6×Molar mass of C)+(6×Molar mass of H)Molar mass of C6​H6​=(6×Molar mass of C)+(6×Molar mass of H) =(6×12)+(6×1)=72+6=78 g/mol=(6×12)+(6×1)=72+6=78g/mol Now, moles of 𝐶6𝐻6=MassMolar mass=3978=0.5 molmoles of C6​H6​=Molar massMass​=7839​=0.5mol
2. Calculate the heat energy change: Given: Δ𝐻=3264.6 kJ/molΔH=3264.6kJ/mol So, heat energy change for 0.5 moles of 𝐶6𝐻6C6​H6​: Heat energy change=Δ𝐻×moles of 𝐶6𝐻6Heat energy change=ΔH×moles of C6​H6​ =3264.6×0.5=1632.3 kJ=3264.6×0.5=1632.3kJ

Since the enthalpy change is given per mole, we have to multiply it by the number of moles of 𝐶6𝐻6C6​H6​ to get the total heat energy change. So, the heat energy change when 39 g of 𝐶6𝐻6C6​H6​ is burnt in an open container will be +1632.3 kJ/kg mole+1632.3kJ/kg mole. Therefore, the correct answer is +1632.3 kJ/kg mole+1632.3kJ/kg mole.