Question

What is the enthalpy of precipitation for the reaction between 50 mL of 0.2 M AgNO3 and 50 mL of 0.2 M NaCl? Given that the final volume of the solution is 100 mL and the temperature remains constant at 25°C.

Answer 1

To calculate the enthalpy of precipitation for the reaction between AgNO and NaCl, we first need to write the balanced chemical equation for the reaction:AgNO aq  + NaCl aq   AgCl s  + NaNO aq Next, we need to determine the limiting reactant. Since both solutions have the same concentration  0.2 M  and volume  50 mL , they will react in a 1:1 ratio, and neither is in excess.Now, we need to find the moles of the limiting reactant:moles = Molarity  Volumemoles = 0.2 mol/L  0.050 L = 0.010 mol  for both AgNO and NaCl The enthalpy of precipitation  H  can be found using the standard enthalpy of formation  Hf  values for each compound in the reaction. The standard enthalpy of formation values at 25C are as follows:Hf AgNO  = -124.4 kJ/molHf NaCl  = -411.12 kJ/molHf AgCl  = -127.01 kJ/molHf NaNO  = -365.6 kJ/molWe can use these values to calculate the enthalpy of precipitation using Hess's Law:H =  Hf products  -  Hf reactants H = [ 1 mol  -127.01 kJ/mol  +  1 mol  -365.6 kJ/mol ] - [ 1 mol  -124.4 kJ/mol  +  1 mol  -411.12 kJ/mol ]H =  -127.01 - 365.6  -  -124.4 - 411.12 H = -492.61 + 535.52H = 42.91 kJ/molTherefore, the enthalpy of precipitation for the reaction between 50 mL of 0.2 M AgNO and 50 mL of 0.2 M NaCl is 42.91 kJ/mol.