Answer:
+26.6kJ/mol
Explanation:
The enthalpy of dissolution of NH₄NO₃ is:
NH₄NO₃(aq) + ΔH → NH₄⁺ + NO₃⁻
Where ΔH is the heat of reaction that is absorbed per mole of NH₄NO₃,
The moles that reacts in 1.60g are (Molar mass NH₄NO₃:80g/mol):
1.60g * * (1mol / 80g) = 0.02 moles reacts
To find the heat released in the coffee cup calorimeter, we must use the equation:
Q = m×ΔT×C
Where Q is heat released,
m is mass of the solution
ΔT is change in temperature (Final temperature - Initial temperature)
C is specific heat of the solution (4.18J/g°C)
Mass of the solution is:
1.60g + 75g = 76.60g
Change in temperature is:
25.00°C - 23.34°C = 1.66°C
Replacing:
Q = m×ΔT×C
Q = 76.60g×1.66°C×4.18J/g°C
Q = 531.5J
This is the heat released per 0.02mol. The heat released per mole (Enthalpy change for the dissolution of NH₄NO₃) is:
531.5J / 0.02mol = 26576J/ mol =
+26.6kJ/mol
+ because the heat is absorbed, the reaction is endothermic-
