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LeilaNami
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Finding volume needed for buffer (URGENT!)
What volume of 0.50M NaClO must be added to 0.20M HClO in order to prepare 500mL of a NaClO/HClO buffer with pH=7.00. Ka(HClO)= 3.5e-8
I'm using the H-H equation pH=pKa + log ([A]/[HA])
NaClO being A and HClO being HA
I tried doing it by method mentioned in another thread but I still did not get the right answer (answer is supposed to be NaClO = 61mL)
pKa= -log(3.5e-8) = 7.46
Using H-H found that [A]/[HA] = .35
mols A = mols HA (.35)
(mols A + mols HA)/.5 = .2
(.35 mols HA + mols HA)/.5 = .2
1.35 mols HA / .5 =.2
mols of HA = 7.4e-2 mols
mols A = (7.4e-2)(.35) = 2.58e-2 mols
.5= 2.58e-2/ L
L= 5.16e-2
mL = 51.6
Close but no cigar. What am I doing wrong?
I have a midterm tomorrow and I've been trying to solve this problem for 5 hours now and I feel like crying I am so frustrated. Please help!
Homework Statement
What volume of 0.50M NaClO must be added to 0.20M HClO in order to prepare 500mL of a NaClO/HClO buffer with pH=7.00. Ka(HClO)= 3.5e-8
Homework Equations
I'm using the H-H equation pH=pKa + log ([A]/[HA])
NaClO being A and HClO being HA
The Attempt at a Solution
I tried doing it by method mentioned in another thread but I still did not get the right answer (answer is supposed to be NaClO = 61mL)
pKa= -log(3.5e-8) = 7.46
Using H-H found that [A]/[HA] = .35
mols A = mols HA (.35)
(mols A + mols HA)/.5 = .2
(.35 mols HA + mols HA)/.5 = .2
1.35 mols HA / .5 =.2
mols of HA = 7.4e-2 mols
mols A = (7.4e-2)(.35) = 2.58e-2 mols
.5= 2.58e-2/ L
L= 5.16e-2
mL = 51.6
Close but no cigar. What am I doing wrong?
I have a midterm tomorrow and I've been trying to solve this problem for 5 hours now and I feel like crying I am so frustrated. Please help!
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