I\'ve provided the answers, I need to know how to get there. Thanks! For the fol

Question

I've provided the answers, I need to know how to get there. Thanks!

For the following 3 buffer procedures, calculate how much of each ingredient is needed. For each buffer procedure you will have a solid (g) ingredient, a liquid (mL) ingredient, and water Show all work Procedure 2 Prepare 50 mL of acetic acid buffer at strength of 0.1 M and at a pH of 5.0 using 1 M acetic acid, sodium acetate, and water Procedure 3 Prepare 50 mL of TRIS buffer at strength of 0.1 M and at a pH of 7.5 using Tris, 1 MHCI and water Formula weight (g/mol) 121.1 Buffer pKa TRIS 8.3 Calculate the weight of the solid buffer you would need to make 50 mL of 0.1 M solution. Procedure 3: 0.602g Tris In 20ml Record pH Procedure 2: 0.262g Sodium Acetate Add HCI dropwise until a pH of7 1.8ml Acetic Acid Total volume 50m Bring up to 50ml Record pH Compare to 4.31ml HCl calculated

Explanation / Answer

Preparation of buffer

Procedure 2 : 50 ml of acetic acid buffer of pH 5.0, strength 0.1 M

Using Hendersen-Hasselbalck equation,

pH = pKa + log(sodium acetate/acetic acid)

5.0 = 4.75 + log(sodium acetate/acetic acid)

(sodium acetate) = 1.8(acetic acid)

we have,

(acetic acid) + (sodium acetate) = 0.1 M x 50 ml = 5 mmol

substituting from above,

(acetic acid) + 1.8(acetic acid) = 5 mmol

(acetic acid) = 5/2.8 = 1.8 mmol

Volume of acetic acid needed = 1.8 mmol/1 M = 1.8 ml

(sodium acetate) needed = 5 mmol - 1.8 mmol = 3.2 mmol

mass of sodium acetate required = 3.2 mmol x 82.03 g/mol/1000 = 0.262 g

Procedure 3 : 50 ml of TRIS buffer of pH 7.5, strength 0.1 M

Using Hendersen-Hasselbalck equation,

pH = pKa + log(TRIS/TRIS.HCl)

7.5 = 8.3 + log(TRIS/TRIS.HCl)

(TRIS) = 0.16(TRIS.HCl)

we have,

(TRIS.HCl) + (TRIS) = 0.1 M x 50 ml = 5 mmol

substituting from above,

(TRIS.HCl) + 0.16(TRIS.HCl) = 5 mmol

(TRIS.HCl) = 5/1.16 = 4.31 mmol

Volume of HCl needed = 4.31 mmol/1 M = 4.31 ml

(TRIS) needed = 5 mmol x 121.1 g/mol/1000 = 0.605 g

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