I need help computing target masses of acid, base and salt needed to prepare an

Question

I need help computing target masses of acid, base and salt needed to prepare an assigned buffer.
Here is all the information:
Ph 7 is my target pH M [buffer]: 0.0200 M [nacl]: 0.100 Volume in L: 0.100
I need help in calculations so I can prepare an assigned buffer properly.
I need help computing target masses of acid, base and salt needed to prepare an assigned buffer.
Here is all the information:
Ph 7 is my target pH M [buffer]: 0.0200 M [nacl]: 0.100 Volume in L: 0.100
I need help in calculations so I can prepare an assigned buffer properly.

Here is all the information:
Ph 7 is my target pH M [buffer]: 0.0200 M [nacl]: 0.100 Volume in L: 0.100 Ph 7 is my target pH M [buffer]: 0.0200 M [nacl]: 0.100 Volume in L: 0.100
I need help in calculations so I can prepare an assigned buffer properly.

Explanation / Answer

pH = 7 target

total concentration of buffer =0.2 M

concentration of NaCl = 0.1

Total Volume 0.1 M

so...

first, choose a buffer with pKa nea that solution

choose HClO since it has a pkA of 7.46

then

apply buffer equation:

pH = pKa + loG(OCl-/HOCl)

that is;

7 = 7.46 + log(ratio)

note that OCl- + HOCl = 0.02

then

ratio = 10^(7-7.46) = 0.346736

OCl-/HOCl = 0.346736

OCl- = 0.346736*HClO

and

OCl- + HOCl = 0.02

so

0.346736*HClO + HOCl = 0.02

so

1.346736*HOCl = 0.02

HOCl = 0.02/1.346736 = 0.01485

OCl- = 0.346736*HClO =0.346736*0.01485

[OCl-] = 0.00514

note that this is concentration, we need masses so:

V = 0.1 L

so

mol = MV = 0.01485*0.1 = 0.001485 mol of HClO

mol = MV = 0.00514*0.1 = 0.000514 mol of ClO- or NaOCl

so

mass of HClO required = mol*MW = 0.001485 *52.46 = 0.07790 g = 77.9 mg HClO

mass of NaOClrequired = mol*MW = 0.000514 *74.44 = 0.03826216 g = 38.26 mg NaClO

for NaCl mass:

mol = MV = 0.1*0.1 = 0.001

mass = mol*MW = 0.001*58.8 = 0.0588 = 58.8 mg of Nacl in 0.1 L

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