Final answer:
The change in enthalpy for the reaction can be calculated using the heat absorbed or released by the water and the number of moles of water. By plugging in the given values and using the formulas, we find that the change in enthalpy is -0.49 kJ. The correct answer is b) - 0.49 kj.
Step-by-step explanation:
The change in enthalpy (ΔH) can be calculated using the formula:
ΔH = q / n
Where q is the heat absorbed or released by the water and n is the number of moles of water.
To calculate q, we can use the formula:
q = mcΔT
Where m is the mass of water, c is the specific heat capacity of water, and ΔT is the change in temperature. Plugging in the given values:
m = 25.0 g
c = 4.184 J/g ℃
ΔT = -4.7 ℃ (negative because the temperature decreases)
Substituting these values into the equation, we get:
q = (25.0 g) * (4.184 J/g ℃) * (-4.7 ℃) = -492.78 J
Finally, we can calculate ΔH by dividing q by the number of moles of water:
ΔH = (-492.78 J) / (18.01528 g/mol) = -0.49 kJ
Therefore, the change in enthalpy for the reaction is -0.49 kJ, so the correct answer is (b) - 0.49 kJ.