Students conducted an experiment to determine ΔH for the reaction between sodium hydroxide and hydrochloric acid - HSC - SSCE Chemistry - Question 26 - 2022 - Paper 1

To calculate the heat energy released, we need to find the change in temperature ( ΔT) and the mass of the solution.

1. Calculate ΔT:

   • Average initial temperature of the solutions:

     $T_{avg} = \frac{21.0 + 21.2}{2} = 21.1 °C$

   • Change in temperature:

     $ΔT = 24.4 °C - 21.1 °C = 3.3 K$

2. Calculate mass of the final solution:

   • Mass of HCl solution = 100.7 g
   • Mass of NaOH solution = 102.0 g
   • Total mass of solution = 100.7 g + 102.0 g = 202.7 g = 0.2027 kg

3. Use the specific heat capacity of water:

   • Specific heat capacity of water = 4.18 x 10³ J K⁻¹ kg⁻¹

4. Calculate heat energy (q):

   • Using the formula:

     $q = mcΔT$ where m is mass, c is specific heat capacity, and ΔT is temperature change.

   $q = 0.2027 kg imes 4.18 \times 10^3 J K^{-1} kg^{-1} \times 3.3 K = 2796 J = 2.8 kJ$