This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Stability of Coordination Compounds”.
1. The degree of ________ between the metal ion and the ligand directly influences the stability of the complex in solution.
Explanation: The magnitude of the equilibrium constant for the association quantitatively expresses the stability of the complex in solution.
2. How are the stepwise stability constants (K) related to the overall stability constant (β)?
a) βn = K1 + K2 + …. + Kn
b) βn = K1 x K2 x … x Kn
c) βn = logK1 + logK2 + …. + logKn
d) βn = 1/(K1 + K2 + …. + Kn)
Explanation: The overall stability constant is the product of all the stepwise stability constants of each individual reaction.
3. If the values of stepwise stability constants for a series of successive reactions are logK1 = 4, logK2 = 3.2, logK3 = 2.7 and logK4 = 2, what is the value of β4?
b) 7.94 x 1011
c) 1.47 x 105
Explanation: logβ4 = logK1 + logK2 + logK3 + logK4
\(\Rightarrow\)log10β4 = 4 + 3.2 + 2.7 + 2 = 11.9
\(\Rightarrow\)β4 = antilog(11.9)
\(\Rightarrow\)β4 = 7.94 x 1011
4. If β is the formation constant, then the instability constant = ________
a) 1 – β
b) β – 1
Explanation: The instability constant is also known as the dissociation constant. It is defined as the reciprocal of the formation or stability constant.
5. For a particular complex, the dissociation equilibrium constant is given as 2.3 x 10-9. What will be the overall stability constant for this complex?
a) 4.35 x 10-10
b) 4.35 x 1010
c) 4.35 x 10-8
d) 4.35 x 108
Explanation: Formation constant = 1/(dissociation constant)
\(\Rightarrow\)β = 1/(2.3 x 10-9)
\(\Rightarrow\)β = 4.35 x 108
6. Two complexes A and B have dissociation constants 1.0 x 10-12 and 4.7 x 10-14 respectively. Which complex will be more stable?
c) Both are equally stable
d) Cannot be determined
Explanation: The smaller the value of dissociation constant, more stable the complex will be in solution. Since 4.7 x 10-14 < 1.0 x 10-12, complex B is more stable.
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