Buffer Solutions

• Now solve the weak acid/conjugate base system:

• HF H3O+ F-

  Initial 1.100 0 0.400
  
  Change -x +x +x
  Equil. 1.100 - x x 0.400 + x

• x(0.400 + x)/(1.100 - x) = 7.0 x 10- 4

• Assume x << 0.400 and 1.100:

  x(0.400)/1.100 = 7.0 x 10- 4
  

• x = 1.93 x 10-3, so the assumption was okay

• pH = -log(1.93 x 10-3) = 2.714

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