[Wienerbroed]

I need help with the following question:

"Benzoic acid (C7H5O2H) has a pK_a of 4,20 at 25,0 °C".
A: What is the pH if 12,21 grams of sodium benzoate is mixed in with 4,00 liters of water (25,0 °C)?
B: If 10,00 milliliters of 10,00 M sodium hydroxide is added, what does the pH become?

[Borek]

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