Chemistrymedium · Past Paper
What is the concentration of $OH^-$ ions in a solution with pH 9?
A$10^{-9}$ mol/L
B$10^{-5}$ mol/L
C$10^9$ mol/L
D$10^5$ mol/L
✓ Correct Answer: B — $10^{-5}$ mol/L
At 25°C, pH + pOH = 14. If pH=9, pOH=5, so [OH-] = $10^{-5}$.
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