Question

Calculate the standard heat of mixing when 50 mL of 1 M HCl is mixed with 100 mL of 1 M NaOH at 25°C. The standard heat of neutralization of 1 M HCl and 1 M NaOH is -57.32 kJ/mol.

Answer 1

To calculate the standard heat of mixing, we first need to determine the number of moles of HCl and NaOH that are reacting.Number of moles of HCl =  concentration of HCl  x  volume of HCl Number of moles of HCl =  1 mol/L  x  50 mL  x  1 L/1000 mL  = 0.05 molNumber of moles of NaOH =  concentration of NaOH  x  volume of NaOH Number of moles of NaOH =  1 mol/L  x  100 mL  x  1 L/1000 mL  = 0.1 molSince HCl and NaOH react in a 1:1 ratio, the limiting reactant is HCl with 0.05 mol. Therefore, 0.05 mol of HCl will react with 0.05 mol of NaOH.Now we can calculate the heat of mixing using the standard heat of neutralization:Heat of mixing =  moles of HCl  x  standard heat of neutralization Heat of mixing =  0.05 mol  x  -57.32 kJ/mol  = -2.866 kJThe standard heat of mixing when 50 mL of 1 M HCl is mixed with 100 mL of 1 M NaOH at 25C is -2.866 kJ.