Answer :
Final answer:
The enthalpy change for the dissolution of hydrogen bromide in water is calculated to be approximately 82.75 kJ/mol HBr, which indicates it is an exothermic reaction.
Explanation:
To calculate the enthalpy change (H) for this chemistry question, you first need to determine the amount of heat transferred using the equation q = mcΔT, where m is the mass of water, c is the specific heat capacity of water (4.18 J/g°C), and ΔT is the change in temperature.
Hence, q = (39.1 g * 4.18 J/g°C * (27.28°C - 20°C)) = 1196.58 J.
Since 1KJ = 1000 J, the heat absorbed by the water is 1.19658 kJ.
You then calculate the moles of HBr by dividing the mass by the molar mass (1.17 g / 80.91 g/mol = 0.01446 mol).
Finally, you calculate the enthalpy change (in kJ/mol HBr) by dividing the heat absorbed by the moles of HBr (1.19658 kJ / 0.01446 mol = 82.75 kJ/mol).
Thus, the enthalpy change H is 82.75 kJ/mol HBr, which indicates this is an exothermic process, as the reaction released heat to the environment.
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