Question

Please, provide the answer with the whole calculations.

1- Calculate the minimum number of theoretical plates necessary to provide a resolution of 1.8 between two peaks arriving after 333.00 and 347.00 seconds.

A- 162.

B- 26161

C- 26200

D- 10000

E- 163

F- 161

2- A chromatogram with ideal Gaussian bands has a Retention time of 9.0 minutes and w1/2 of 2,0 minutes. How many theoretical plates are present?

A- 1.1 x10²

B- 6.2

C- 6.22

D- 1.12x10²

E- 12

F-2.24x10²

G- 2.2x10²

H- 24.9

Q- 25

W- 12.4

3- A chromatogram with ideal Gaussian bands has a Retention time of 9.0 minutes and w1/2 of 2,0 minutes. What is the plate height if the column is 0.10 m long?

A- 0.09cm

B- 0.892 cm

C- 0.08 m

D- 0.089 cm

E- 0.09 mm

F- 0.089 mm

4- If Volume 1 = 20.0 ml, Volume 2 = 25.0 ml and K = 3.25, what percentage of S remains in phase 1? which S means solvent.

A- 20

B- 19.8

C- 0.200

D- 0.197

5- If Volume 1 = 20 ml, Volume 2 = 22.0 ml and K = 3.25, what percentage of S remains in phase 1 if this process is repeated 3 times? Which S means solvent.

A- 1.044

B- 0.01044

C- 1.0

D- 1.04

6- A chromatographic procedure separates 100 mg of unknown mixture on a column of length 40 cm and diameter 4.25 cm. If instead we had only 4.0 mg of the material, what size column would you use to separate the same mixture?

A- 0.85 cm

B- 0.17 cm

C- 17.0 cm

D- 17 cm

E- 8.5 cm

Answer 1

1) The dead time, t₀ is required to calculate the number of plates.

2) The half width is given as w_1/2 = 2.0 min and the retention time is t_R = 9.0 min.

The number of theoretical plates is given as

N = 5.54*(t_r/w_1/2)²

Plug in values and obtain

N = 5.54*[(9.0 min)/(2.0 min)]²

= 5.54*(4.5)²

= 112.185

≈ 1.1*10²

1. is the correct answer.

3) The number of plates, N is given as N = 1.1*10².

The height equivalent to theoretical plates is given as

N = L/HETP

where L = length of the column and HETP = height equivalent to theoretical plates.

Given H = 0.10 m and N = 112.185, we have,

HETP = (0.10 m)/(112.185)

= 8.9138*10^-4 m

= (8.9138*10^-4 m)(1 mm)/(1.0*10^-3 m) [1 mm = 1.0*10^-3 m]

= 0.89138 mm

= (0.89138 mm)*(1 cm)/(10 mm) [1 cm = 10 mm]

= 0.089138 cm ≈ 0.089 cm

(D) is the correct answer.