Question
I just did a chemistry lab relating to enthalpy of reactionand Hess's law. In this lab, tne enthaply changes for the reactionof ammonia and HCl was determined using Hess's law. The purpose ofthe lab was to verify the Hess's Law. If the enthalply change forthe reaction between sodium hydroxide and HCl and reaction betweensodium hydroxide and ammonium chlride are determined, then theenthalpy change for the reaction between ammonia and hydrochloricacid are calculated. equation 1: NaOH + HCl --> NaCl + H20 equation 2: NH4Cl + NaOH --> NH3 + NaCl + H2O equation 3: NH3 + HCl --> NH4Cl What would be a real life application where the enthaply ofreaction can be determined by using Hess's Law? I just did a chemistry lab relating to enthalpy of reactionand Hess's law. In this lab, tne enthaply changes for the reactionof ammonia and HCl was determined using Hess's law. The purpose ofthe lab was to verify the Hess's Law. If the enthalply change forthe reaction between sodium hydroxide and HCl and reaction betweensodium hydroxide and ammonium chlride are determined, then theenthalpy change for the reaction between ammonia and hydrochloricacid are calculated. equation 1: NaOH + HCl --> NaCl + H20 equation 2: NH4Cl + NaOH --> NH3 + NaCl + H2O equation 3: NH3 + HCl --> NH4Cl What would be a real life application where the enthaply ofreaction can be determined by using Hess's Law?
Explanation / Answer
Using rxnH for equation 1&equation 2then you can calculate the rxnH for equation 3 , advantage ofHess Law . NaOH + HCl --> NaCl + H2O ...........>I , H1 = xkJ NH4Cl + NaOH --> NH3 + NaCl + H2O......>II , H2 = ykJ For the reverse reaction , H2 issame in but reverse in sign . NH3 + NaCl + H2O ..........> NH4Cl +NaOH ......> III , H3 =-H2 = -ykJ Now, III+I will gives us NH3 + HCl --> NH4Cl with H = H1+ H3 =xkJ - ykJ