Q. What is the [OH⁻] in the final solution prepared by mixing 20.0 mL of 0.050 M HCl with 30.0 mL of 0.10 M Ba(OH)₂?
A) 0.40 M
B) 0.0050 M
C) 0.12 M
D) 0.10 M
Explanation
[Solution from source] HCl gives 20 × 0.050 = 1.0 mmol H⁺; Ba(OH)₂ gives 30 × 0.10 × 2 = 6.0 mmol OH⁻. After neutralisation 5.0 mmol OH⁻ remain in 50 mL: [OH⁻] = 0.10 M. Forgetting that Ba(OH)₂ gives two OH⁻ per formula unit leads to a wrong value. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.