|Acid-Base Worksheet #5|
|1.||Write ionic equations that illustrate how each pair of compounds can serve as a buffer pair.|
|(a) H2CO3 and NaHCO3 (the "carbonate" buffer in blood)|
|(b) NaH2PO4 and Na2HPO4 (the "phosphate" buffer inside body cells)|
|(c) NH4Cl and NH3
|2.||Show that the equation can be rewritten as|
|3.||Which buffer would be better able to hold a steady pH on the addition
of strong acid, buffer 1 or buffer 2? Explain.
Buffer 1: a solution containing 0.10 M NH4Cl and
1 M NH3. Buffer 2: a solution containing 1 M NH4Cl
and 0.10 M NH3.
|4.||How many grams of sodium acetate, NaC2H3O2,
would have to be added to 1 L of 0.15 M acetic acid (pKa=4.74)
to make the solution a buffer for pH 5.00?
|5.||How many grams of sodium formate, NaCHO2, would have
to be dissolved in 1.0 L of 0.12 formic acid (pKa) to make the
solution a buffer for pH 3.80?
|6.||What ratio of molar concentrations of NH4Cl and NH3
would buffer a solution at pH 9.25?
|7.||To study the effect of a weakly acidic medium on the rate of corrosion
of a metal, a chemist prepared a buffer solution by making it 0.11 M NaC2H5O2
and also 0.090 M HC2H3O2. What is the pH
of this solution?
|8.||How is the pH of a buffered solution related to the pKa of the weak acid in the buffer if|
|(a) the ratio of [anion] to [acid] is 10 to 1?|
|(b) The ratio of [anion] to ]acid] is 1 to 10?
|9.||A solution of acetic acid is pink in the presence of the indicator methyl orange. When solid sodium acetate is added to the acid solution, the colour changes to yellow. Why?|