Acid–base Equilibria
A 0.10 M solution of a weak base B has Kb = 2.5×10⁻⁴. The pOH of the solution is approximately:
Select the correct option:
Solution
2.40
- Formula: For a weak base, [OH−]=Kb⋅C.
- Values: Kb=2.5×10−4, C=0.1M.
- Calculation:
- [OH−]=(2.5×10−4)×10−1=2.5×10−5.
- [OH−]=25×10−6=5×10−3M.
- pOH Calculation:
- pOH=−log(5×10−3)
- pOH=3−log5=3−0.699=2.301.
- Selection: Among the choices, 2.40 is the closest approximation (often using slightly different precision).
🔒 Solution Hidden from View
Submit your answer to unlock the detailed step-by-step solution.
More acid–base equilibria Practice Questions
The conjugate base of HSO₄⁻ is:
The conjugate base of HSO₄⁻ is:
Calculate [H+] (in mol L⁻¹) after mixing 25 mL of 0.040 M HCl with 75 mL of water (assume volumes ad...
Calculate [H+] (in mol L⁻¹) after mixing 25 mL of 0.040 M HCl with 75 mL of water (assume volumes ad...
Which change increases the pH of an acetic acid/sodium acetate buffer the most?
Which change increases the pH of an acetic acid/sodium acetate buffer the most?
The percent dissociation of a 1.0×10⁻³ M solution of a weak monoprotic acid (Ka = 1.0×10⁻⁵) is appro...
The percent dissociation of a 1.0×10⁻³ M solution of a weak monoprotic acid (Ka = 1.0×10⁻⁵) is appro...
The conjugate acid of (CH3)3 N is:
The conjugate acid of (CH3)3 N is:
Which factor most strongly determines whether an amphoteric species acts as an acid or a base in wat...
Which factor most strongly determines whether an amphoteric species acts as an acid or a base in wat...
About This Question
- Subject
- chemistry
- Chapter
- equilibrium
- Topic
- acid–base equilibria
- Difficulty
- Hard
- Year
- 2025
Solution
Correct Answer:
2.40
- Formula: For a weak base, [OH−]=Kb⋅C.
- Values: Kb=2.5×10−4, C=0.1M.
- Calculation:
- [OH−]=(2.5×10−4)×10−1=2.5×10−5.
- [OH−]=25×10−6=5×10−3M.
- pOH Calculation:
- pOH=−log(5×10−3)
- pOH=3−log5=3−0.699=2.301.
- Selection: Among the choices, 2.40 is the closest approximation (often using slightly different precision).
This hard difficulty chemistry question is from the chapter equilibrium, covering the topic of acid–base equilibria. It appeared in the 2025 exam.
Looking for more practice? Explore all chemistry questions or browse equilibrium questions on RankGuru.