Final answer:
To calculate the Kb for ethylamine, we can use the relationship between pH and Ka, the ionization constant for an acid. In this case, ethylamine is a weak base, so we need to find the pOH using the given pH. We can then calculate the concentration of hydroxide ions, [OH-], and finally the Kb using the equation: Kw = Ka × Kb = [H+][OH-].
Step-by-step explanation:
To calculate the Kb for ethylamine, we can use the relationship between pH and Ka, the ionization constant for an acid. In this case, ethylamine is a weak base, so we need to find the pOH using the given pH. We can then calculate the concentration of hydroxide ions, [OH-], and finally the Kb using the equation: Kw = Ka × Kb = [H+][OH-]. Let's see how it works.
- Given: pH = 11.87. We can calculate the pOH using the equation pH + pOH = 14: pOH = 14 - 11.87 = 2.13.
- The concentration of hydroxide ions, [OH-], can be calculated using the equation: [OH-] = 10^(-pOH). [OH-] = 10^(-2.13) = 0.0071 M.
- Finally, we can calculate the Kb using the equation: Kw = Ka × Kb = [H+][OH-]. Since Kw = 1.0 × 10^(-14) at 25°C, we can solve for Kb. Let's substitute the known values: 1.0 × 10^(-14) = (1.0 × 10^(-14)) × Kb = (1.0 × 10^-14) × (0.0071 M). Solving for Kb, we find that it is approximately 1.41 × 10^(-13).