Scoring a Lab 1: 100 marks PRELAB: 10 marks Labwork 20 marks Lab Notebook 10 mar

Question

Scoring a Lab 1: 100 marks PRELAB: 10 marks Labwork 20 marks Lab Notebook 10 marks ASSIGNMENT: 10 marks 1.Show calculations for making following reagents 1Pt A 200 ml of a 1 M solution of Tris (molecular weight 121.1 g/mol) 1Pt B. 300 ml of 0.2M EDTA (MW 372.2 g/mol) c. 200 ML of TE buffer (contains 10 mM Tris and 1 mm EDTA) using solutions made inAand.B 2. A solution containing a concentration of 0.01M (H+) ions will have a pH of1Pt 3. What is the Henderson Hasselbach equation? Use this equation to explain the relation 2 Pt between pH and dissociation constants. Henderson Hasselbach H pa [HA] the logof the U thu conjugate loast Conentrathon ot w 4. Use the above equation to calculate the p of buffer in tube 5. Hint. Use the Henderson Hasselbach equation to substitute known values 1 pt

Explanation / Answer

1.

a.

M = (W/MW)(1000/V)

W = (M X MW X V)/100

= (1 X 121.1 X 200)/1000

= 24.22 g

b.

W = (M X MW X V)/100

= (0.2 X 372.2 X 300)/1000

= 22.332 g

c.

C1V1 = C2V2

V1 = C2V2/C1

For tris,

C1 = 1 M

C2 = 10 mM = 0.01 M

V2 = 200 mL

V1 = (0.01 X 200)/1 = 2 mL

For EDTA,

C1 = 0.2 M

C2 = 1 mM = 0.001 M

V2 = 200 mL

V1 = (0.001 X 200)/0.2 = 1 mL

So, Mix 2 mL of 1 M tris and 1 mL of 0.2 M EDTA. Make up the volume to 200 mL to prepare the given solution.

2.

pH = -log[H+]

= -log[0.01]

= 2

3.

pH = pKa + log[A-]/[HA]

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