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Using tabulated Ka and Kb values, calculate the pH of the following solutions. 

1. A solution containing 2.5×10-1 M HCOOH and 3.0×10-1 M HCOONa.

For HCOOH, Ka = 1.8×10-4.

2.     650.0 mL of solution containing 16.0 g of HNO2 and 50.0 g of NaNO2.

For HNO2Ka = 4.0×10-4.

Feb 18th, 2015

1.  HCOOH <===> COOH- + H+

I.    2.5e-1                3e-1           0

C.  -x                         +x           +x

E.  2.5e-1 -x           3e-1 +x      x

Ka = (3e-1 +x)*x / (2.5e-1 -x) = 1.8e-4

x = 1.125e-5

pH = - log(1.125e-5)  = 4.95

2.  Work exactly the same way after calculating the molarity of the initial concentrations.

Feb 19th, 2015

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