In an experiment, 1.2 g of sodium hydroxide pellets, NaOH(s), were dissolved in 100 mL of water at 25?C.
The temperature of the water rose to 27.5?C.
Calculate the enthalpy change (heat of solution) for the reaction in kJ mol-1 of solute.

Are we supposed to add 100 and 1.2 OR dont add them.
Below solution is correct?
q = mass(water) ? specific heat capacity(water) ? change in temperature(solution)
q = m(H2O(l)) ? cg(H2O(l)) ? (Tf - Ti)
q = 100 ? 4.184 ? (27.5 - 25) = 1046 J

Quote from: prasamb@yahoo.com on December 11, 2022, 07:54:17 PM

Calculate the enthalpy change (heat of solution) for the reaction in kJ mol-1 of solute.

Are we supposed to add 100 and 1.2 OR dont add them.
Below solution is correct?
q = mass(water) ? specific heat capacity(water) ? change in temperature(solution)
q = m(H2O(l)) ? cg(H2O(l)) ? (Tf - Ti)
q = 100 ? 4.184 ? (27.5 - 25) = 1046 J

We will not add 1.2 g NaOH in volume as we assume in these type of questions change in volume is negligible.
Otherwise they will mention they density of solutions.
Your method is correct.
∆H _reaction   = - q_water / n moles of NaOH