please answer A and B part B says: Does delta U = delta H for the combustion of

Question

please answer A and B
part B says:
Does delta U = delta H for the combustion of oxalic acid? why or why not?

Thanks Problem 5 (20 points): The combustion of oxalic acid (H C204) in a bomb calorimeter (as sketched in the right) yields 2816 J g' at 25C. Molecules in the gas phase may be treated as ideal gases. Motorized strrer Electrical leads for gniting sample H C 04 (s) + 1/20: (g)2CO2 (g)+ HO(g) a) Calculate ayo and H for the combustion of 1 mol of oxalic acid (M = 90.0 g mol-1). iniet Bomb (reaction chamber) Fine wire in contact with sample Cup holding sample Water b) Does -AHo for the combustion of oxalic acid? Why or why not?

Explanation / Answer

for the case of constant volume bomb calorimeter, change in internal energy = 2816 J/gm

molar mass of oxalic acid = 90 g/mole

hence change in internal energy/mole, deltaU= 2816 J/gm* 90gm/mole= 253440 j/mole=253.44 Kj/mole

since Enthalpy (H)= U+PV

deltaH= deltaU+ delta(PV)

deltaH= deltaU+ RT*deltan

deltan= change in no of gaseous moles during the reaction = 2+1-0.5= 2.5

hence deltaH= 253440+8.314*298*2.5 =259634 J/mole=259.634 Kj/mole

since there mole of gaseous products not same as moles of gaseous reactants, deltaU is not equal to deltaH.

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