Preparing a Buffer Calculate the number of grams of ammonium chloride that must
ID: 943541 • Letter: P
Question
Preparing a Buffer
Calculate the number of grams of ammonium chloride that must be added to 2.00 L of a 0.500 M ammonia solution to obtain a buffer of pH = 9.20. Assume the volume of the solution does not change as the solid is added. Kb for ammonia is 1.80×105.
Calculate the number of grams of ammonium chloride that must be added to 2.00 of a 0.500 ammonia solution to obtain a buffer of pH = 9.20. Assume the volume of the solution does not change as the solid is added. for ammonia is .
60.7 g 30.4 g 1.52 g 0.568 g 1.59×105 gExplanation / Answer
pOH = pKb + log(conjugate/base)
pKb = -logKb= 4.74
V = 2 L
M = 0.4
pOH = 14-pH = 4.8
pOH = pKb + log(conjugate/base)
4.8 = 4.74 + log(conjugate/0.5)
conjugate = (10^(4.8-4.74)) * 0.5
copnjugate = 0.574 M
mol = MV = 0.574*2 = 1.148 mol fo NH4Cl
mass = mol*MW = 1.148*53.491 = 61.407668 g of NH4Cl
nearest answe is 60.7 g