How many moles of sodium acetate must be added to 2.0 L of 0.10 M acetic acid to give a solution that has a pH equal to 5.00? Ignore the volume change due to the addition of sodium acetate.

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How many moles of sodium acetate must be added to 2.0 L of 0.10 M acetic acid to give a solution that has a pH equal to 5.00? Ignore the volume change due to the addition of sodium acetate.  Ka of acetic acid is 1.7×10-5.

0.3396 moles

Explanation:

pH = pKA + log

[acetic acid] = 0.1 M

pH = 5.0

=

5.0 = -log () + log

5.0 = 4.77 + log [acetate] + 1

5.0 = 5.77 + log [acetate]

- log [acetate] = 5.77 - 5.0

- log [acetate]  = 0.77

log [acetate]  = -0.77

[acetate]  = log⁻¹ (-0.77)

[acetate]  =  0.1698

∴ for 2L = 2 × 0.1698

= 0.3396 moles