Acid–base Equilibria

Question

50 mL of 0.10 M HCl is mixed with 25 mL of 0.20 M NaOH at 25°C. The pH of the resulting solution is:

RankGuru · Accepted Answer

1. **Reactants**: $HCl$ (strong acid) and $NaOH$ (strong base).
2. **Moles of $HCl$**: $n_{H^+} = 0.050 	ext{ L} 	imes 0.10 	ext{ M} = 0.005$ mol.
3. **Moles of $NaOH$**: $n_{OH^-} = 0.025 	ext{ L} 	imes 0.20 	ext{ M} = 0.005$ mol.
4. **Neutralization**: $H^+ + OH^- 	o H_2O$. Since the moles of acid and base are exactly equal, complete neutralization occurs.
5. **State of Solution**: The solution contains $NaCl$ and $H_2O$. $NaCl$ is a salt of a strong acid and a strong base and does not undergo hydrolysis.
6. **pH**: The resulting solution is neutral. At $25^\circ C$, the $pH = **7.00$**.

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Acid–base Equilibria

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