The pH of 0.004 M hydrazine solution is 9.7. Its ionization constant (...
Introduction:
Hydrazine (N2H4) is a weak base that can ionize in water to form the hydrazine ion (N2H5+) and hydroxide ion (OH-). The ionization constant of hydrazine, also known as Kb, is a measure of the extent to which it ionizes in water.
Given:
Concentration of hydrazine solution (N2H4) = 0.004 M
pH of the solution = 9.7
Calculating the pOH:
pOH is the negative logarithm of the hydroxide ion concentration. It can be calculated using the formula:
pOH = 14 - pH
In this case, the pH is 9.7, so the pOH is:
pOH = 14 - 9.7 = 4.3
Calculating the hydroxide ion concentration (OH-):
The hydroxide ion concentration can be determined using the pOH value and the formula:
[OH-] = 10^(-pOH)
In this case, the pOH is 4.3, so the hydroxide ion concentration is:
[OH-] = 10^(-4.3)
Calculating the hydrazine ion concentration (N2H5+):
Since hydrazine (N2H4) ionizes to form the hydrazine ion (N2H5+), the concentration of the hydrazine ion can be assumed to be equal to the hydroxide ion concentration:
[N2H5+] = [OH-] = 10^(-4.3)
Calculating the concentration of hydrazine (N2H4):
To calculate the concentration of hydrazine (N2H4), we can use the equation for Kb:
Kb = [N2H5+][OH-] / [N2H4]
Substituting the known values:
Kb = (10^(-4.3) * 10^(-4.3)) / 0.004
Simplifying the expression:
Kb = 10^(-8.6) / 0.004
Calculating the value of Kb:
Kb = 2.5 x 10^(-7)
Conclusion:
The ionization constant (Kb) of the 0.004 M hydrazine solution is 2.5 x 10^(-7).