When 0.485 g of compound x is burned completely in a bomb calorimeter containing 3000 g of water, a temperature rise of 0.285°c is observed. what is δu of the reaction for the combustion of compound x? the hardware component of the calorimeter has a heat capacity of 3.81 kj/°c. the specific heat of water is 4.184 j/g·°c, and the mw of x is 56.0 g/mol.
a. -538 kj/mol
b. 4660 kj/mol
c. -4660 kj/mol
d. 538 kj/mol

a. -538 kJ/mol

Explanation:

Internal energy change (ΔU) for the reaction of combustion in the bomb calorimeter is:

ΔU = q calorimeter + q solution

Where:

q calorimeter is Ccal×ΔT, (Ccal=3,81kJ/°C) and (ΔT is 0,285°C)

q solution is c×m×ΔT (c= 4.184 J/g°C), (m=3000g H₂O), (ΔT is 0,285°C)

Replacing:

ΔU = 1,09kJ + 3,58kJ = 4,67 kJ

This energy is per 0,485g of X, now, per mole of X

= -539kJ/mol ≡ a. -538 kJ/mol

-negative because the energy is produced by rising of temperature-

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