Sodium CItrate Tribasic ( MW: 294.1 grams)
Sodium CItrate Dibasic ( MW: 263.11 grams)
pKa3 of citric acid: 6.396.
Sodium Citrate Dibasic is the weak acid and Sodium Citrate Tribasic is the conjugate base
Total concentration of buffer = 0.050 M
[Sodium Citrate Dibasic] + [Sodium Citrate Tribasic] = 0.050 M ...(1)
According to Henderson-Hasselbalch equation,
pH = pKa + log([conjugate base] / [weak acid])
pH = pKa3 + log([Sodium Citrate Tribasic] / [Sodium Citrate Dibasic])
6.00 = 6.396 + log([Sodium Citrate Tribasic] / [Sodium Citrate Dibasic])
log([Sodium Citrate Tribasic] / [Sodium Citrate Dibasic]) = 6.00 - 6.396
log([Sodium Citrate Tribasic] / [Sodium Citrate Dibasic]) = -0.396
[Sodium Citrate Tribasic] / [Sodium Citrate Dibasic] = 10-0.396
[Sodium Citrate Tribasic] / [Sodium Citrate Dibasic] = 0.4 ... (2)
Solving equations (1) and (2) simultaneously, we get
[Sodium Citrate Dibasic] = 0.03567 M
[Sodium Citrate Tribasic] = 0.01433 M
moles Sodium Citrate Dibasic = (molarity Sodium Citrate Dibasic) * (volume of buffer in Liter)
moles Sodium Citrate Dibasic = (0.03567 M) * (0.1 L)
moles Sodium Citrate Dibasic = 0.003567 mol
mass Sodium Citrate Dibasic = (moles Sodium Citrate Dibasic) * (molar mass Sodium Citrate Dibasic)
mass Sodium Citrate Dibasic = (0.003567 mol) * (263.11 g/mol)
mass Sodium Citrate Dibasic = 0.938 g
moles Sodium Citrate Tribasic = (molarity Sodium Citrate Tribasic) * (volume of buffer in Liter)
moles Sodium Citrate Tribasic = (0.01433 M) * (0.1 L)
moles Sodium Citrate Tribasic = 0.001433 mol
mass Sodium Citrate Tribasic = (moles Sodium Citrate Tribasic) * (molar mass Sodium Citrate Tribasic)
mass Sodium Citrate Tribasic = (0.001433 mol) * (294.1 g/mol)
mass Sodium Citrate Tribasic = 0.421 g
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weak acid must be combined with how many grams of the
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1.00 L of a buffer that is 1.00 M
in the weak base?
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