Question

Activity 4: Observations and Interpretations NHCl(s) + H2O(l) + NH(aq) + Cl(aq) 1) What did you observe when you added the concentrated HCl solution to the saturated solution of ammonium chloride? White crystal precipitate formed 2) Interpret the observation in 1, in terms of the equation given above and LeChateliers Principle. 3) What did you observe when you placed this test tube in the boiling water bath? By adding heat, the precipitate went back into solution and is now a clear colourless liquid again. 4) Based on your observations in 3, which of the reactions in the equilibrium, written above, is endothermic and which is exothermic? Explain. 5) What temperature change did you observe when ammonium chloride was dissolved in water? Before: room temperature After cold 6) What does such a temperature change indicate, and is this consistent with what you observed in 3? Explain. After: cold When the ammonium chloride dissolved in water, the temperature fell because the ammonium chloride pulled heat from the water causing the temperature to decrease. Thus, the energy change is endothermic.
please help with 2, 4, 6. thanks!!

Answer 1

2) As here concentrated HCl solution is added to a saturated solution of NH4Cl , the amount of Cl- is increased. So, products will be converted into reactants for the above reaction . As a  result of that solid NH4Cl will be produced which appear as white crystal precipitate.

4) By adding heat, The precipitate went back into solution and is now a colourless liquid again. So, by adding heat the above reaction goes to the forward direction and more NH4+ and Cl- are produced. This forward equilibrium is endothermic and backward equilibrium is exothermic while adding concentrated HCl.

6) The temperature will be decreased as a result of the forward reaction because NH4Cl pulled heat from the water since the forward equilibrium is endothermic . And with adding heat the forward reaction favours and more NH4+ and Cl- are produced.