Question

Calculate the heat of mixing when 100 mL of 0.1 M HCl is mixed with 200 mL of 0.2 M NaOH at 25°C. The specific heat of the solution is 4.18 J/g°C and the density of the solution is 1.00 g/mL. Assume that the heat capacity of the solution is equal to that of pure water.

Answer 1

To calculate the heat of mixing, we first need to determine the amount of heat released during the neutralization reaction between HCl and NaOH. The balanced chemical equation for this reaction is:HCl aq  + NaOH aq   NaCl aq  + H2O l The heat of neutralization for a strong acid and strong base reaction is approximately -57.32 kJ/mol. We need to find the limiting reactant to determine the number of moles of water formed in the reaction.Moles of HCl =  0.1 M    100 mL    1 L / 1000 mL  = 0.01 molMoles of NaOH =  0.2 M    200 mL    1 L / 1000 mL  = 0.04 molSince HCl is the limiting reactant, the number of moles of water formed is equal to the moles of HCl:Moles of H2O = 0.01 molNow we can calculate the heat released during the reaction:q = moles of H2O  heat of neutralizationq = 0.01 mol  -57.32 kJ/mol = -0.5732 kJSince the heat of mixing is equal to the heat released during the reaction, the heat of mixing is -0.5732 kJ.