Answer:
[tex]\Delta H=-0.02\ kJ[/tex]
Explanation:
The expression for the calculation of the enthalpy change of a process is shown below as:-
[tex]\Delta H=m\times C\times \Delta T[/tex]
Where,
[tex]\Delta H[/tex] is the enthalpy change
m is the mass
C is the specific heat capacity
[tex]\Delta T[/tex] is the temperature change
Thus, given that:-
Mass of ammonium nitrate = 1.25 g
Specific heat = 4.18 J/g°C
[tex]\Delta T=21.9-25.8\ ^0C=-3.9\ ^0C[/tex]
So,
[tex]\Delta H=-1.25\times 4.18\times 3.9\ J=-20.3775\ J[/tex]
Negative sign signifies loss of heat.
Also, 1 J = 0.001 kJ
So,
[tex]\Delta H=-0.02\ kJ[/tex]