Answer:
ΔErnx = -6384.55 kJ/mol
Step-by-step explanation:
A bomb calorimeter operates at a constant volume.
I.e ΔV = 0.
The first law of thermodynamics states that, energy can neither be created nor destroyed, but may be converted from one form to another.
Mathematically,
ΔU = ΔH + pΔV
Where ΔU = change in internal Energy, ΔH = Heat adsorbed or evolved and pΔV = work done by the system.
since a bomb calorimeter operates with constant volume,
∴ ΔV=0 as such, pΔV=0.
Then, ΔU = ΔH
This can be written as
ΔE = qv .
Where qv is the heat flowing out from the reaction towards the surrounding water at constant volume.
qv = 5.86 Kj/⁰c × (29.4-25.8)
qv = 5.86 × 3.6
qv = 21.096 kJ.
∴ ΔE of the solution = 21.096 kJ.
Because combustion is an exothermic reaction,
qv = -ΔE
and ΔErnx = -ΔE/ no of moles.
-ΔE = -21.096 kJ.
no moles of (C₁₂H₁₀) = mass of(C₁₂H₁₀)/molar mass of (C₁₂H₁₀)
mass of(C₁₂H₁₀) = 0.514g
molar mass of (C₁₂H₁₀) = (12×12) +(1×10) = 144+10 = 154g/mol.
∴ no of mole of (C₁₂H₁₀) = 0.514/154
≈ 0.0033 mol.
∴ΔErnx = -21.096/0.0033
ΔErnx ≈ -6386.55 kJ/mol
ΔErnx = -6384.55 kJ/mol