Answer:
pH = 2.87
Explanation:
When NaOH reacts with HF NaF and H2O are produced:
NaOH + HF → NaF + H2O
That means after the reaction moles of NaF are equal to moles of NaOH added and moles of HF are initial moles of HF - moles of NaOH added:
<em>Moles NaOH = Moles NaF:</em>
0.050L * (0.20mol/L) = 0.01 moles of NaF
<em>Moles HF:</em>
0.050L * (0.60mol/L) = 0.03 moles HF = Initial moles
0.03 moles - 0.01 moles = 0.02 moles HF
To find pH we need to use H-H equation to determine pH of the buffer:
pH = pKa + log [NaF] / [HF]
<em>Where pH is pH of the buffer</em>
<em>pKa is pKa of HF-NaF buffer: 3.17</em>
<em>And [] could be taken as moles of each species.</em>
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That is:
pH = 3.17 + log [0.01] / [0.02]
<h3>pH = 2.87</h3>
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