Search:
The calorimeter $(C$ $=$ $ 202,5 \;J/K)$ with an electronic thermometer. The calorimeter is at room temperature: $21,9 ^oC$. The $250\; mL$ graduated cyclinders contain $0,5\; M$ solutions of $NaOH$ and $HCl$.
$Q$ $=$ $-4185 \cdot m_{water} \cdot (θ_f-θ_i)$ $-$ $C_{calorimeter}(θ_f-θ_i)$
$Q$ $=$ $-4185 \cdot 0,5\cdot (28,3-21,9)$ $-$ $202,5(28,3-21,9)$
$Q$ $=$ $-12092,8\; J$ for a reaction of $0,5\cdot 0,5$ $=$ $0,25 \;mol \;OH^-$ with an equal number of moles $HCl$
The reaction $H^+(aq)$ $ +$ $ OH^-(aq)$ $ \longrightarrow $ $H_2O$ liberates (measured by our rather simple apparatu) $4\cdot 12092,8 $ $= $ $48371,2\; J$ ≅ $48,7 \;kJ$ The correct value is about $10$ % higher.