various household substances, study the properties of buffer he amount of acetic
ID: 1036853 • Letter: V
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various household substances, study the properties of buffer he amount of acetic acid and epare the buffers and test their CE112L-05 Spring 2018 Pre-Lab Questions pH and ? I. During this part #3 of the lab, you will make 2 acetic acid buffer solutions (HC2H3O2/NaC2H3O2) of the same pH (pH 4.0), but with different concentration of the components. Use the Henderson-Hasselbalch equation to perform the following calculations. The K, of acetic acid is 1.8 x 105 Buffer A: Calculate the mass of the solid sodium acetate (NaC2H302) required to mix with 100 ml of 0.1 M acetic acid (HC2H302), to prepare a pH 4 buffer. Record the mass in the table, part 3 of this experiment. a. Buffer B: Calculate the mass of the solid sodium acetate (NaC2H302) required to mix with 100 ml of 1.0 M acetic acid (HC2H3O2), to preparea pH 4 buffer. Record the mass in the table, part 3 of this experiment. b.Explanation / Answer
no of moles of CH3COOH = molarity * volume in L
= 0.1*0.1 = 0.01moles
no of moles of CH3COONa = x
PKa = -logKa
= -log1.8*10^-5
= 4.75
PH = 4
PH = Pka + log[CH3COONa]/[CH3COOH]
4 = 4.75 + logx/0.01
logx/0.1 = 4-4.75
logx/0.01 = - 0.75
x/0.01 = 10^-0.75
x/0.01 = 0.1778
x = 0.1778*0.01
x = 0.001778
no of moles of CH3COONa = 0.001778moles
mass of CH3COONa = no of moles * gram molar mass
= 0.001778*82 = 0.1458g
no of moles of CH3COOH = molarity * volume in L
= 1*0.1 = 0.1moles
no of moles of CH3COONa = x
PKa = -logKa
= -log1.8*10^-5
= 4.75
PH = 4
PH = Pka + log[CH3COONa]/[CH3COOH]
4 = 4.75 + logx/0.1
logx/0.1 = 4-4.75
logx/0.1 = - 0.75
x/0.1 = 10^-0.75
x/0.1 = 0.1778
x = 0.1778*0.1
x = 0.01778
no of moles of CH3COONa = 0.01778moles
mass of CH3COONa = no of moles * gram molar mass
= 0.01778*82 = 1.458g
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