Calculate the ph of a buffer solution containing 0.2M NH4OH and 0.25M NH4Cl kb=1.8×10
Use the Henderson-Hasselbalch equation.
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Calculate the pH of a buffer solution containing 0.2 mole of nh4cl and 0.1 mole of nh4oh per litre. KB for nh4oh=1.85×10
To calculate the pH of a buffer solution, we need to consider the concentration of the conjugate acid-base pair and their equilibrium constant.
In this case, we have NH4OH (ammonium hydroxide) as the base and NH4Cl (ammonium chloride) as the conjugate acid. The equilibrium reaction can be written as:
NH4OH ⇌ NH4+ + OH-
The equilibrium constant, Kb, for this reaction is given as 1.8×10^-5.
First, we need to determine the amount of NH4+ and OH- ions in the solution. Since the concentration of NH4OH is given as 0.2 M, the concentration of NH4+ ions will also be 0.2 M.
To calculate the concentration of OH- ions, we can use the Kb expression:
Kb = [NH4+][OH-] / [NH4OH]
Since we know the concentration of NH4+ ions and Kb, we can rearrange the equation to find [OH-]:
[OH-] = Kb * [NH4OH] / [NH4+]
Substituting the given values, we get:
[OH-] = (1.8×10^-5) * (0.2) / (0.2)
[OH-] = 1.8×10^-5 M
Now that we have the concentration of OH- ions, we can calculate the pOH using the formula:
pOH = -log10([OH-])
pOH = -log10(1.8×10^-5)
pOH ≈ 4.74
Next, we need to calculate the pH of the buffer solution using the relation:
pH = 14 - pOH
pH = 14 - 4.74
pH ≈ 9.26
Therefore, the pH of the buffer solution containing 0.2 M NH4OH and 0.25 M NH4Cl is approximately 9.26.