Question

Calculate the enthalpy change when 50 ml of 0.2 M sodium chloride solution is mixed with 50 ml of 0.1 M silver nitrate solution. Given the enthalpy of precipitation of silver chloride as -64.8 kJ/mol.

Answer 1

To calculate the enthalpy change, we first need to determine the amount of silver chloride  AgCl  that will be formed when the two solutions are mixed. The balanced chemical equation for the reaction is:AgNO3 aq  + NaCl aq   AgCl s  + NaNO3 aq First, we need to find the moles of each reactant:Moles of NaCl =  Volume  Molarity  =  0.050 L  0.2 mol/L  = 0.01 molMoles of AgNO3 =  Volume  Molarity  =  0.050 L  0.1 mol/L  = 0.005 molSince the stoichiometry of the reaction is 1:1, the limiting reactant is AgNO3, as there are fewer moles of it. Therefore, 0.005 mol of AgCl will be formed.Now, we can calculate the enthalpy change using the enthalpy of precipitation of silver chloride:Enthalpy change = moles of AgCl  enthalpy of precipitation per moleEnthalpy change = 0.005 mol   -64.8 kJ/mol  = -0.324 kJThe enthalpy change for the reaction is -0.324 kJ.