I need help with these questions. All of the mixtures are stated in the second i
ID: 1032286 • Letter: I
Question
I need help with these questions. All of the mixtures are stated in the second image.
48 QUESTIONS FOR A SOLUBILITY INVESTIGATION Write the equilibrium reaction for the mixture in the beaker in Part A, step 2. 1. Write the net ionic equation for the reaction (which involves one of the species in the reaction that you've just written) that occurs when nitric acid is added to the beaker in Part A. Examine the two reactions shown above for part A and explain, using Le Châtelier's principle, why the changes occurred in the beaker after adding nitric acid. 2. Write the equilibrium reaction for the mixture in the beaker in Part B, step 2. As in question 1, write the net ionic equation for the reaction (which involves one of the species in the reaction that you've just written) that occurs when aqueous ammonia is added to the beaker in Part B Again, according to Le Châtelier's principle, why does the precipitate dissolve upon addition of ammonia? As above, write the net ionic equation for the reaction that occurs when nitric acid is added to the beaker in part B. As previously, explain why the precipitate reappears upon addition of nitric acid 3. Write the net ionic equation for the reaction that initially occurs when aqueous sodium hydroxide is added to the zinc nitrate solution. (Formation of the amphoteric hydroxide.) Write the net ionic equation for the reaction that occurs when an excess of sodium hydroxide is added to the amphoteric hydroxide. (Step 4) Write the net ionic equation for the reaction that occurs when nitric acid is added to the amphoteric hydroxide. (Step 5) In the context of part C of this experiment, explain what an amphoteric hydroxide can do that: acetic acid can do aquéous ammonia can't do sodium chloride can't doExplanation / Answer
1) The species present in the mixture are calcium chloride (CaCl2) and sodium oxalate (Na2C2O4). The equilibrium reaction is given as
CaCl2 (aq) + Na2C2O4 (aq) ---------> CaC2O4 (s) + 2 NaCl (aq)
Nitric acid (HNO3) reacts with CaC2O4 as below
CaC2O4 (s) + 2 HNO3 (aq) --------> Ca(NO3)2 (aq) + H2C2O4 (aq)
The net ionic equation for the reaction is
CaC2O4 (s) + 2 H+ (aq) --------> Ca2+ (aq) + H2C2O4 (aq)
CaC2O4 is an insoluble salt and the solubility product is given as
Ksp = [Ca2+][C2O42-]
When HNO3 is added to the solution, the protons (H+) combine with oxalate (C2O42-) ions forming oxalic acid (H2C2O4) which is poorly ionized in aqueous solution. Hence, [C2O42-] decreases. Since Ksp is an equilibrium constant (must remain constant at a particular temperature), more CaC2O4 goes into solution producing C2O42-. Thus, the solubility of CaC2O4 increases; infact, CaC2O4 is completely soluble in strong mineral acids.
2) The species present in the mixture are silver nitrate (AgNO3) and sodium chloride (NaCl). The chemical reaction is given as
AgNO3 (aq) + NaCl (aq) ---------> AgCl (s) + NaNO3 (aq)
Aqueous ammonia (NH3) reacts with solid AgCl to form soluble silver diamine complex as below.
AgCl (s) + 2 NH3 (aq) ----------> [Ag(NH3)2]+Cl- (aq)
The solubility of AgCl is given as
AgCl (s) -------> Ag+ (aq) + Cl- (aq)
The equilibrium constant is given as
Ksp = [Ag+][Cl-]
When ammonia is added to AgCl, Ag+ combines with NH3 to form soluble silver diamine complex. This reduces [Ag+]. In order to keep Ksp constant, more AgCl dissolves; therefore, the solubility of AgCl increases on addition of NH3.
Nitric acid (HNO3) reacts with ammonia forming soluble ammonium nitrate and AgCl as below.
[Ag(NH3)2]+Cl- (aq) + HNO3 (aq) ---------> AgCl (s) + NH4NO3 (aq)
Due to the formation of soluble ammonium nitrate, the complex splits up giving more Ag+. This increases [Ag+]. To keep Ksp constant, the equilibrium favors the reverse reaction, producing more AgCl.