The pH Problems Dec 27_ 2010

# The pH Problems Dec 27_ 2010 - The pH of 0.20 M HCN is 5.00...

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The pH of 0.20 M HCN is 5.00. Calculate the Ka for HCN [H + ] = 10 -pH = 10 -5.00 = 0.0000100 M HCN D H + + CN - I 0.20 M 0 0 C 0.0000100 M 0.0000100 M 0.0000100 M E 0.19999 0.0000100 M 0.0000100 M Ka = (0.0000100) 2 = 5.0 x 10 -10 0.19999 Ka = 5.0 x 10 -10 2. The pH of 2.20 M HF is 1.56. Calculate the Ka for HF. Ka = 3.5 x 10 -4 3. The pH of 0.805 M CH 3 COOH is 2.42. Calculate the Ka for CH 3 COOH. Ka = 1.8 x 10 -5 4. The pH of 1.65 M H 3 BO 3 (a triprotic) is 4.46. Calculate the Ka for H 3 BO 3 . Note a triprotic weak acid only loses one proton. Ka = 7.3 x 10 -10

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5. The pH of a 0.10 M diprotic acid is 3.683, calculate the Ka and identify the acid. [H + ] = 10 -pH = 10 -3.683 = 0.0002075 M H 2 X D H + + HX - Note a diprotic weak acid only loses one proton. I 0.10 M 0 0 C 0.0002075 M 0.0002075 M 0.0002075 M E 0.09979 0.0002075 M 0.0002075 M Ka = (0.0002075) 2 = 4.3 x 10 -7 0.09979 Ka = 4.3 x 10 -7 Carbonic acid H 2 CO 3 Look up on Ka Table. 6.
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The pH Problems Dec 27_ 2010 - The pH of 0.20 M HCN is 5.00...

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