Question

Calculate the enthalpy change of precipitation when 50 mL of 0.1 M calcium chloride solution is mixed with 50 mL of 0.1 M silver nitrate solution, assuming that the reaction goes to completion and the temperature remains constant at 25°C.

Answer 1

To calculate the enthalpy change of precipitation, we first need to determine the balanced chemical equation for the reaction between calcium chloride  CaCl  and silver nitrate  AgNO . The reaction is a double displacement reaction, and the products are silver chloride  AgCl  and calcium nitrate  Ca NO  :CaCl aq  + 2AgNO aq   2AgCl s  + Ca NO  aq Next, we need to determine the moles of each reactant. We can do this using the volume and molarity of each solution:moles of CaCl = volume  molarity = 0.050 L  0.1 mol/L = 0.005 molmoles of AgNO = volume  molarity = 0.050 L  0.1 mol/L = 0.005 molNow, we need to determine the limiting reactant. Since the stoichiometry of the reaction is 1:2  1 mole of CaCl reacts with 2 moles of AgNO , we can see that AgNO is the limiting reactant, as there are not enough moles of AgNO to react with all the moles of CaCl.Next, we need to find the enthalpy change for the reaction. We can do this using the enthalpy of formation values for each compound:Hf CaCl  = -795 kJ/molHf AgNO  = -123 kJ/molHf AgCl  = -127 kJ/molHf Ca NO   = -641 kJ/molNow, we can calculate the enthalpy change for the reaction using the following equation:H =  Hf products  -  Hf reactants H = [ 2  -127  +  -641 ] - [ -795  +  2  -123 ]H =  -254 - 641  -  -795 - 246 H = -895 + 1041H = 146 kJ/molSince the limiting reactant is AgNO, and there are 0.005 moles of it, we can now calculate the enthalpy change for the reaction:H = 146 kJ/mol  0.005 mol = 0.73 kJTherefore, the enthalpy change of precipitation when 50 mL of 0.1 M calcium chloride solution is mixed with 50 mL of 0.1 M silver nitrate solution is 0.73 kJ.