Map A General Chemistr University Science Books presented by Sapling Learning Do

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Map A General Chemistr University Science Books presented by Sapling Learning Donald McQuarrie. Peter A. Rock. Ethan Gallogly Calculate the change in pH when 6.00 mL of 0.100 M HCl(aq) is added to 100.0 mL of a buffer solution that is 0.100 M in NH3(aq) and 0.100 M in NH4Cl(aq). A list of ionization constants can be found here. Number ApH Calculate the change in ph when 6.00 mL of 0.100 M NaOH(aq) is added to the original buffer solution. Number ApH C Previous ® Up & View solution Check Answer Next Exit Give

Explanation / Answer

The original buffer equation (basic)

pOH = pKb + log(conjugate/base)

pKb = -log(Kb) = -log(1.8*10^-5)

pKb = 4.75

then

conjugate = MV = 100*0.1 = 10 mmol

base = MV = 100*0.1 = 10 mmol

then

pOH = 4.75 +log(10/10) = 4.75

pH = 14-4.75 = 9.25

b)

after adding acid (H+)

mmol H+= MacVac = 6*0.1 = 0.6 mmol

then

mmol of conjugate = 10 + 0.6 = 10.6

mmol of base = 10 - 0.6 = 9.4

then

pOH = 4.75 + log(10.6/9.4) = 5.775

pH = 14-5.775 = 8.225

c)

after adding base (OH-)

mmol OH- = MacVac = 6*0.1 = 0.6 mmol

then

mmol of conjugate = 10 - 0.6 = 9.4

mmol of base = 10 + 0.6 = 10.6

then

pOH = 4.75 + log(9.4/10.6) = 4.6978

pH = 14-4.6978= 9.3022

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