Answer:
(1). Check Explanation.
(2). Kc = 8.0 × 10^-12.
Explanation:
Step one: write out the balanced ionic dissociation equation.
Zn(CN)2(s) <======> Zn^2+ + 2CN^-.
The reaction above is an equilibrium Reaction and the ksp value= 8.0 x 10-12.
Step 2 : add Hydrogen ion(from the acid) to the cyanide ion, CN^-. [The cyanide ion is a Bronsted- Lowry's base and it has the tendency of accepting hydrogen ion to form HCN, which is a weak acid].
2 CN^- + 2H3O^+ <====> 2 HCN + 2H2O.
The ka value of HCN = 6.2 x 10^-10. Therefore, the K =( 1/ ka)^2 = 1/ 6.2 x 10^-10 = (1.6 × 10^-11)^2 = 2.6 ×10^-22.
ANSWER TO THE FIRST PART OF THE QUESTION ==> Zn(CN)2 is an ionic compound and it contains a basic anion therefore the solubilty increases in the presence of a strong acid.
ANSWER TO THE SECOND PART OF THE QUESTION : We will now add the equation in step one and step two together to give us the equilibrium constant,Kc.
Therefore, we now have;
Zn(CN)2(s) + 2H3O^+ <===> HCN + 2CN^- + H2O. Kc = 8.0 × 10^-12.
Answer:
Explanation:
The task above seeks to test your knowledge of solubility of ionic compounds.
Here are some factors that affect the solubility of ionic compounds;
• addition of an ion common to the equilibrium causes a decrease in the solubility of a sparingly soluble salt.
• pH
• formation of complex ions,
The knowledge of the concept above can help you to demonstrate
how these factors when properly manoeuvred can be used to isolate one metal ion from a mixture in solution.
To solve the task above here are the steps needed
1. Consider the dissolution of Zn(CN)_2(s).
Zn(CN)_2(s) ◀—–▶ Zn2+ + 2CN-
ksp =[Zn2+][CN-]² = 8.0 x 10-12.
In a saturated solution, Zn2+
and CN- are in equilibrium with solid Zn(CN)_2.
If a strong acid is added to the solution, the cyanide ion can react to form the Hydrogen cyanide and
water
2 CN- + 2H3O+ ◀——▶ 2 HCN + 2H2O
K = 1/Ka(HCN))
From the tables;
Ka of HCN = 6.2 × 10^ - 10.
K = (1/ka)² = (1/ 6.2 x 10^-10) = (1.6 × 10^-11)^2 = 2.6 ×10^-22.
Zn(CN)_2 contains a basic anion so its solubility increases in the presence of acid. Use Ksp[Zn(CN)_2] and Ka to
calculate the overall equilibrium constant for this reaction.
Adding these two equilibrium reactions shows the effect of adding a strong acid to a saturated Zn(CN)_2 solution
