calculate the [oh-] in 0.01m aqueous solution of NaOCN {Kb for OCN- is...
Calculation of [OH-] in 0.01M Aqueous Solution of NaOCN
Understanding the Problem
In this problem, we are given a 0.01M aqueous solution of NaOCN. Our task is to calculate the concentration of hydroxide ions ([OH-]) in this solution. We are also given the value of Kb for OCN- which is 10^(-10).
Writing the Chemical Equation
NaOCN is a salt of a weak acid (HCN) and a strong base (NaOH). Therefore, it will undergo hydrolysis in water to form HCN and OH- ions. The chemical equation for this reaction is:
NaOCN + H2O ↔ HCN + NaOH
Writing the Equilibrium Expression
Using the above chemical equation, we can write the equilibrium expression for this reaction as follows:
Kb = [HCN][OH-] / [OCN-]
Using the Given Information to Find [OH-]
As we are given the value of Kb for OCN-, we can use this value to find the concentration of OH- ions in the solution.
Kb = 10^(-10) = [HCN][OH-] / [OCN-]
[HCN] = [NaOH] = 0.01 M (as NaOH is a strong base and is completely dissociated)
[OCN-] = [NaOCN] = 0.01 M (as NaOCN is completely dissociated)
Substituting these values in the equilibrium expression, we get:
10^(-10) = [HCN][OH-] / [OCN-]
10^(-10) = (0.01)([OH-]) / 0.01
[OH-] = 10^(-8)
Therefore, the concentration of hydroxide ions in the given solution is 10^(-8) M.
Conclusion
Using the given information and the concept of hydrolysis, we were able to calculate the concentration of hydroxide ions in the given solution. The value of Kb for OCN- helped us to relate the concentrations of various species in the equilibrium expression and solve for the unknown concentration.