Question

Calculate the standard enthalpy change for the precipitation reaction between lead(II) nitrate and sodium chloride to form lead(II) chloride and sodium nitrate. The balanced chemical equation for the reaction is:Pb(NO3)2 (aq) + 2NaCl (aq) → PbCl2 (s) + 2NaNO3 (aq)

Answer 1

To calculate the standard enthalpy change for the precipitation reaction, we need the standard enthalpies of formation  Hf  for each compound involved in the reaction. The standard enthalpies of formation are as follows:Pb NO3 2  aq : -379.5 kJ/molNaCl  aq : -407.3 kJ/molPbCl2  s : -359.4 kJ/molNaNO3  aq : -365.6 kJ/molNow, we can use Hess's Law to calculate the standard enthalpy change for the reaction:H = [Hf products  - Hf reactants ]H = [1 mol   -359.4 kJ/mol  + 2 mol   -365.6 kJ/mol ] - [1 mol   -379.5 kJ/mol  + 2 mol   -407.3 kJ/mol ]H = [ -359.4  + 2   -365.6 ] - [ -379.5  + 2   -407.3 ]H =  -359.4 - 731.2  -  -379.5 - 814.6 H = -1090.6 + 1194.1H = 103.5 kJ/molThe standard enthalpy change for the precipitation reaction between lead II  nitrate and sodium chloride to form lead II  chloride and sodium nitrate is 103.5 kJ/mol.