Calculate the number of grams of CH3COONa * 3H2O (sodium acetate tri-hydrate) needed to make 250.0 mL of a CH3COOH (acetic acid)/ CH3COONa * 3H2O buffer. The target pH of the buffer is 5.25. The given concentration of [CH3COOH] is equal to 0.10 M. Ka = 1.80 x 10-5 for acetic acid.

10.88 g

Explanation:

We have:                            

[CH₃COOH] = 0.10 M

pH = 5.25

Ka = 1.80x10⁻⁵      

V = 250.0 mL = 0.250 L

The pH of the buffer solution is:  

   (1)

By solving equation (1) for [CH₃COONa*3H₂O] we have:  

Hence, the mass of the sodium acetate tri-hydrate is:

Therefore, the number of grams of CH₃COONa*3H₂O needed to make an acetic acid/sodium acetate tri-hydrate buffer solution is 10.88 g.

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