1.You have to make 0.200 M acetate buffer by mixing 69.0 mL of the 0.200 M sodiu

Question

1.You have to make 0.200 M acetate buffer by mixing 69.0 mL of the 0.200 M sodium acetate solution and 50.0 mL of the 0.200 M acetic acid solution. By using Henderson-Hasselbalch equation calculate the pH of this buffer.

2. You have to make tris buffer by mixing 5.0 mL of 0.200 M Tris base and 5.0 mL of 0.200 M Tris- HCl and diluting to a final volume of 100. mL. Tris-HCl is the acidic form, with a pKa of 8.10. Calculate and record the concentration of Tris in the solution. Predict the pH of this buffer by using Henderson-Hasselbach equation.

3. You have to make 100 ml of 0.100M sodium phosphate buffer, pH 11. Please calculate amount of NaH2PO4 base M.W 120g/mol.

Explanation / Answer

1. pH= pKa+ log[salt/acid]

pka of aceticacid = 4.76

pH= 4.76+ log[0.2*69/1000/0.2*50/1000]

= 4.899

2. pH= pKa+ log[salt/acid]

Tris-base pKb = 14-8.10 = 5.9

pOH = pKb + log[salt/acid]

= 5.9 + log[0.2*5/100/0.2*5/100]

= 5.9

pH = 14-5.9 = 8.1

3. amount of NaH2PO4 = 0.1*100/1000 * 120
= 1.2 grams

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