User:Pauline Wonnenberg/Notebook/CHEM 471 Fall 2017/2017/09/05

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Objectives

  • Prepare 5mM NaOH solution
  • Prepare Au:AA ratios over different pH range
  • Make AA titration stock solutions

Description

  • Prepare 5mM NaOH Solution:
Solution prepared through dilution to form a 50mL solution
Calculations
0.10L x 5x10-3M = 5x10-4moles
Molar mass of NaOH=39.99g/mol
Using the M1V1=M2V2 formula:
(1M NaOH)V1=(5nM)(100mL)
V1=5x10-4L NaOH =0.5mL of 1M NaOH


  • Prepare Au:AA:NaOH ratios over different pH range:

Preparation of four 10mL test tubes per amino acid, (1) & (2) using 5mM NaOH and (3) & (4) using 1M NaOH.

  1. 1:1:0.5
  2. 1:1:1
  3. 1:1:0.1
  4. 1:1:1


  • Make AA Titration Stock Solutions:
Phenylalanine = 250x10-6M in 0.0200L
NaOH = 1M in 0.0200L NaOH
To make
0.000250M NaOH
Calculations
((0.0200L Phe)(0.000250M Phe)(1M NaOH))/(0.0200L NaOH) = 0.000250M NaOH
M1V1=M2V2
(1M NaOH)(V1)=(0.000250M NaOH)(0.500L NaOH)
V1=0.125mL of 1M NaOH

Data

  • Prepare Au:AA ratios over different pH range:
Below are the results obtained from preparing Au
AA:NaOH solution over pH 10,11, and 12.






Theoretical pH calculations

Calculate the mole concentration for NaOH:

5mM NaOH mole concentration
1:1:0.5 ratio
0.5x10-3L x 5x10-3M = 2.5x10-6moles of NaOH
1:1:1 ratio
1x10-3L x 5x10-3M = 5x10-6moles of NaOH
1M NaOH mole concentration
1:1:0.1 ratio
0.1x10-3L x 1M = 1x10-4moles of NaOH
1:1:1 ratio
1x10-3L x 1M = 1x10-3moles of NaOH


Convert the concentration to Molarity:

1:1:0.5 ratio (5mM NaOH)
(2.5x10-6)/10mL x 1000mL/1L = 2.5x10-4M
1:1:1 ratio (5mM NaOH)
(5x10-6)/10mL x 1000mL/1L = 5x10-4M
1:1:0.1 ratio (1M NaOH)
(1x10-4)/10mL x 1000mL/1L = 0.01M
1:1:1 ratio (1M NaOH)
(1x10-3)/10mL x 1000mL/1L = 0.1M


Calculate the pOH and the pH for each ratio:

1:1:0.5 ratio (5mM NaOH)
pOH = -log(2.5x10-4) = 3.60
pH = 14 - 3.60 = 10.40
1:1:1 ratio (5mM NaOH)
pOH = -log(5x10-4) = 3.30
pH = 14 - 3.30 = 10.70
1:1:0.1 ratio (1M NaOH)
pOH = -log(0.01) = 2
pH = 14 - 2 = 12
1:1:1 ratio (1M NaOH)
pOH = -log(0.1) = 1
pH = 14 - 1 = 13


UV/Vis of each AA solution:


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