Answer to Question #283639 in Physical Chemistry for Ruru

Question

30g of NaOH was dissolved in 80ml of water.The temperature increased from 27°C to 70°C.Estimate the enthalpy change for the dissolution of NaOH

Answer 1

$\Delta H= mc\Delta T$

Assuming density of solution$= 1g/ml$

and taking $c=4.2kJ/(kg.K)$

$\Delta H = \frac{80}{1000}×4.2×(70-27)$

$=14.448kJ$

Molar enthalpy of dissolution:

$=\frac{40}{30}×14.448=19.264kJ$

$\therefore \Delta H_{diss}=-19.264kJ\>mol^{-1}$