Answer:
ΔErxn = -6212.6kJ/mol
Explanation:
When 0.538 g of biphenyl (C₁₂H₁₀) undergoes combustion in a bomb calorimeter, the temperature rises from 26.1 ⁰C to 29.8 ⁰C.
Δ[tex]E_{rxn}[/tex] for the combustion of biphenyl is 6212.6 kJ/mol.
Given:
The heat capacity of the bomb calorimeter, determined in a separate experiment, is [tex]5.86 kJ/^0C[/tex]
Now, from the formula of Heat of bomb calorimeter
Q=C. ΔT
where, C= capacity of calorimeter, which is given i.e. [tex]5.86 kJ/^0C[/tex].
Consider the value for, ΔT=29.8-26.1= 3.7[tex]^0 C[/tex]
When 0.538 g of biphenyl undergoes combustion in a bomb calorimeter, the temperature rises from 26.1 ⁰C to 29.8 ⁰C.
Therefore, Q=C. ΔT= [tex]5.86 kJ/^0C[/tex] * 3.7[tex]^0 C[/tex]=21.682 kJ
The internal energy change for the reaction ( Δ[tex]E_{rxn}[/tex]) can be calculated as:
Δ[tex]E_{rxn}[/tex] = [tex]\frac{-Q}{moles}[/tex]
Here, we are considering moles of biphenyl.
No. of moles = [tex]\frac{mass}{Molar mass}=\frac{0.568 g}{154.21 g/mol} =0.00349 mol[/tex] (since, molar mass of biphenyl= 154.21 g/mol)
Therefore,
Δ[tex]E_{rxn}[/tex] = [tex]\frac{-21.682kJ}{0.00349 mol} = -6212.6 kJ/mol[/tex]
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