To calculate the heat of mixing, we first need to determine the number of moles of HCl and NaOH that are reacting. Moles of HCl = Volume of HCl x Concentration of HCl Moles of HCl = 50 mL x 0.1 mol/L = 5 mmolMoles of NaOH = Volume of NaOH x Concentration of NaOH Moles of NaOH = 50 mL x 0.1 mol/L = 5 mmolSince the moles of HCl and NaOH are equal, the reaction goes to completion, and all of the HCl and NaOH will react to form water and NaCl.Now, we can calculate the heat of mixing using the heat of neutralization:Heat of mixing = moles of HCl x heat of neutralization Heat of mixing = 5 mmol x -57.5 kJ/mol Since we are working with millimoles, we need to convert the heat of neutralization to kJ/mmol:Heat of mixing = 5 mmol x -57.5 kJ/mol x 1 mol/1000 mmol Heat of mixing = 5 mmol x -0.0575 kJ/mmol Heat of mixing = -0.2875 kJThe heat of mixing when 50 mL of 0.1 M HCl is mixed with 50 mL of 0.1 M NaOH at 25C is -0.2875 kJ.