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buffer Problems 1) A buffer is prepared by adding moles of HC2H3O2 and moles of NaC2H3O2 to enough water to make dm3 of solution. What is the pH? (Ka = x 10-5) 2) What is the pH of a solution prepared by dissolving g of NaHCO3 and g of Na2CO3 in enough water to make a dm3 solution? (Ka = x 10-11) 3) g of NaC9H7O4 is added to 250. mL of a M HC9H7O4 solution. What is the pH of the buffer ? Ka = x 10-5 4) A buffer is made by adding M HC2H3O2 and M NaC2H3O2. If mol of NaOH is added to 125 mL of this buffer , what is the pH? Ka = x 10-5. 5) A buffer is made by adding moles of NH4Br and moles of NH3 to a sufficient amount of water. If moles of HCl are added to the buffer solution, what is the pH? Ka = x 10-10. Solutions 1) na = mol HC2H3O2 V = dm3 nb = mol NaC2H3O2 Ka = x 10-5 [HC2H3O2] = n/V [HC2H3O2] = mol HC2H3O2/( dm3 x 1 L/1 dm3) = M [C2H3O2-] = n/V [C2H3O2-] = mol NaC2H3O2/( dm3 x 1 L/1 dm3) x 1 mol C2H3O2-/ 1 mol NaC2H3O2 = M HC2H3O2(aq) H+(aq) + C2H3O2-(aq) [ ]i 0 [ ]c -x +x +x

Buffer Problems 1) A buffer is prepared by adding 0.60 moles of HC2H3O2 and 2.0 moles of NaC2H3O2 to enough water to make 1.0 dm 3 of solution. What is the pH? (Ka = 1.8 x 10-5) 2) What is the pH of a solution prepared by dissolving 15.0 g of NaHCO3 and 15.0 g of Na2CO3 in enough water to make a 0.250 dm 3 solution? (Ka = 5.6 x 10-11)

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