# school

What is the pH of 0.1 M formic acid solution? Ka=1.7„e10-4?
What is the pH value of buffer prepared by adding 60 ml of 0.1 M CH3COOH to 40 ml of a solution of 0.1 M CH3COONa? What is the pH value of an acetate buffer (pK=4.76) prepared by adding 20 ml of 1 M HCl to 100 ml of a solution of 0.3 M sodium acetate? What is the pH value of a buffer made up of 10 ml of 0.1 M NaHCO3 and 5 ml of 0.14 M H2CO3? The pKa for bicarbonate is 6.1. How would you make 1 l of a 0.1 M acetic acid buffer with a pH=4.9? The MW of acetic acid is 60 g/mole, the MW of sodium acetate is 82 g/mole. The acetate buffer is made by mixing 250 ml of 0.5 M acetic acid and 250 ml of 1 M sodium acetate. What will be the pH value of prepared buffer? The pK of acetic acid is 4.7. Calculate the pH of an acetate buffer composed of 0.2 M sodium acetate and 0.1 M acetic acid? The pKa for acetic acid is 4.76. Solve using the Henderson-Hasselbalch equation?

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1. determine the final concentration of a 20.ml 5.M NaCl solution if 30Mml of water has is added to the solution?

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2. I don't believe I'm in the mood to do all of your buffer homework; however, I'll be glad to help you. The formic acid is done this way. Let's call formic acid, HFo
.............HFo ==> H^+ + Fo^-
initial......0.1......0.....0
change........-x.....x......x
equil.......0.1-x.....x.....x

Ka = (H^+)(Fo^-)/(HFo)
Substitute from the ICE chart above into the Ka expression and solve for x.

For ALL of the buffer problems use the Henderson-Hasselbalch equation. Substitute into pH = pKa + log[(base)/(acid)]

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3. 5M x (20/50) = ? ASSUMING that the volumes are additive; i.e., that 20 mL + 30 mL = 50 mL. Not all solutions are additive.

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