1. Convert the mass of NaOH to moles: \frac{19.9 \, \text{g}}{40.0 \, \text{g/mol}} = 0.4975 \, \text{mol}
2. Calculate the heat released: 0.4975 \, \text{mol} \times -44.51 \, \text{kJ/mol} = -22.14 \, \text{kJ}
3. Convert kJ to J: -22.14 \, \text{kJ} \times 1000 \, \text{J/kJ} = -22140 \, \text{J}
4. Calculate the temperature change:
\Delta T = \frac{-22140 \, \text{J}}{519.9 \, \text{g} \times 4.18 \, \text{J/g}^\circ \text{C}} = -10.23 \, ^\circ \text{C}
5. Determine the final temperature:
25 \, ^\circ \text{C} + (-10.23 \, ^\circ \text{C}) = 14.77 \, ^\circ \text{C}
[Answer] \( 14.77 \, ^\circ \text{C} \)