Use the Henderson-Hasselbalch equation.
pH = pKa + log(base)/(acid)
pKa you know or can look up.
base = mols NaF = grams/molar mass
acid = mols HF = M x L
Solve for pH and take the difference between the new pH and 1.93 to find the change.
Post your work if you get stuck.
The pH of 0.40 M HF(aq) is 1.93. Calculate the change in pH when 0.301 g of sodium fluoride is added to 53.7 mL of the solution. Ignore any change in volume.
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