Chromatography
Liquid Chromatography
Purpose: The purpose of this lab was to separate substances based on their polarity by using liquid chromatography.
Data Table:
Red Dye
Blue Dye
Run#1
Run#2
Run#3
Run#1
Run#2
Run#3
Start of Band(mL)
1.50
2.20
1.00
2.70
3.00
2.00
End of Band(mL)
2.70
3.00
2.00
6.40
5.50
6.00
Beaker
Eluant
Observations
1
H2O
White powder
2
5%isopropyl
Red powder
3
28%isopropyl
Blue powder
4
70%isopropyl
Oily residual
Calculations:
W = Vend – Vstart
Red:
W1 =2.70-1.50= 1.20mL
W2 = 3.00 – 2.20 = 0.80mL
W3 = 2.00 − 1.00 = 1.00mL
Blue:
W1 = 6.40-2.70=3.70mL
W2 =5.50-3.00 =2.50mL
W3 = 6.00-2.00=4.00mL
Wavg red = (1.20+0.80+1.00)/3= 1.00mL
Wavg blue = (3.70+2.50+4.00)/3= 3.40mL
VRave = Vstartave + ½ Wave
Vstartavered = (1.50+2.20+1.00)/3= 1.57mL
Vstartaveblue = (3.00+2.70+2.00)/3=3.57mL
VRave red = 1.57+1.00/2=2.07mL
VRave blue= 3.57+3.40/2=5.27mL
k = (VRave − 0.49mL)/0.49mL kred =(2.07 − 0.49)/0.49= 3.22 kblue = (5.27− 0.49)/0.49=9.76
α = kblue/kred α =9.76/3.22= 3.03
R = (VRave(blue) − VRave(red))/0.5(Wblue +Wred)
R =(5.27− 2.07)/0.5(3.40+1.00)= 1.45
Post Lab Questions:
1. What is meant by polarity of molecules? What causes differences in polarity?
Polarity means unequal electron sharing. One molecule has a greater pull or stronger electronegativity on shared electron compared to the other molecule. The side with the stronger electronegativity will be negative while the molecule with the weaker electronegativity is positive. Differences in polarity are caused by the differences in electronegativity levels (the tendency of an atom to attract electrons when forming a bond) and the alignment of the atoms which can make an uneven electron distribution. 2. In discussing solubility, the rule “like dissolves like” is frequently used. What does this mean?
It means that substances with the same polarity dissolve each other. The general rules are: polar substances dissolve ionic
Purpose: The purpose of this lab was to separate substances based on their polarity by using liquid chromatography.
Data Table:
Red Dye
Blue Dye
Run#1
Run#2
Run#3
Run#1
Run#2
Run#3
Start of Band(mL)
1.50
2.20
1.00
2.70
3.00
2.00
End of Band(mL)
2.70
3.00
2.00
6.40
5.50
6.00
Beaker
Eluant
Observations
1
H2O
White powder
2
5%isopropyl
Red powder
3
28%isopropyl
Blue powder
4
70%isopropyl
Oily residual
Calculations:
W = Vend – Vstart
Red:
W1 =2.70-1.50= 1.20mL
W2 = 3.00 – 2.20 = 0.80mL
W3 = 2.00 − 1.00 = 1.00mL
Blue:
W1 = 6.40-2.70=3.70mL
W2 =5.50-3.00 =2.50mL
W3 = 6.00-2.00=4.00mL
Wavg red = (1.20+0.80+1.00)/3= 1.00mL
Wavg blue = (3.70+2.50+4.00)/3= 3.40mL
VRave = Vstartave + ½ Wave
Vstartavered = (1.50+2.20+1.00)/3= 1.57mL
Vstartaveblue = (3.00+2.70+2.00)/3=3.57mL
VRave red = 1.57+1.00/2=2.07mL
VRave blue= 3.57+3.40/2=5.27mL
k = (VRave − 0.49mL)/0.49mL kred =(2.07 − 0.49)/0.49= 3.22 kblue = (5.27− 0.49)/0.49=9.76
α = kblue/kred α =9.76/3.22= 3.03
R = (VRave(blue) − VRave(red))/0.5(Wblue +Wred)
R =(5.27− 2.07)/0.5(3.40+1.00)= 1.45
Post Lab Questions:
1. What is meant by polarity of molecules? What causes differences in polarity?
Polarity means unequal electron sharing. One molecule has a greater pull or stronger electronegativity on shared electron compared to the other molecule. The side with the stronger electronegativity will be negative while the molecule with the weaker electronegativity is positive. Differences in polarity are caused by the differences in electronegativity levels (the tendency of an atom to attract electrons when forming a bond) and the alignment of the atoms which can make an uneven electron distribution. 2. In discussing solubility, the rule “like dissolves like” is frequently used. What does this mean?
It means that substances with the same polarity dissolve each other. The general rules are: polar substances dissolve ionic