Which of the following statements regarding thin layer chromatography are true? in thin layer chromatography, a polar organic compound will be repelled by the adsorbent and therefore travel not as far up the plate than a non-polar compound in thin layer chromatography, a polar organic compound will be attracted by the adsorbent and therefore travel not as far up the plate as a non-polar compound sample spots should be approximately 1 cm in diameter. covering the sample jar is done to prevent fingerprints on the slide. the rf value will change if the adsorbent material is changed. thin layer chromatography is an example of adsorption chromatography, and not partition chromatography.

a) False

b) True

c) False

d) False

e) True

f) True

Explanation:

a) In thin layer chromatography, a polar organic compound will be repelled by the adsorbent and therefore travel not as far up the plate than a non-polar compound. FALSE. The adsorbent usually is a polar compound that will attract the polar organic compound.

b) In thin layer chromatography, a polar organic compound will be attracted by the adsorbent and therefore travel not as far up the plate as a non-polar compound. TRUE. The polar organic compound will be attracted by the adsorbent doing its travel not as far.

c) Sample spots should be approximately 1 cm in diameter. FALSE. Sample spots must be of 1-2 mm of diameter.

d) Covering the sample jar is done to prevent fingerprints on the slide. FALSE. The covering is doing to saturate the jar's air with solvent.

e) The Rf value will change if the adsorbent material is changed. TRUE. The travel of the compound depends of the retention that is made by the adsorbent material.

f) Thin layer chromatography is an example of adsorption chromatography, and not partition chromatography. TRUE. The mechanism of separation in thin-layer chromatography is differences of adsorption from different compounds.

part 1: the half-life of the element is 22 years.

part 2: it will take 132.02 year for the sample to decay from 308.0 g to 4.8125 g.

explanation:

part 1: there are two ways to determine the half life time.

first way: the half life time can be determined directly from its definition as it is the time required for the sample to decay to its half concentration.

from the data the initial concentration was 45.0 g and decayed to its half value (22.5 g) in 22.0 years.

second way: the radio active decay is considered first order reaction so we can use the laws of first order reactions.

k = (1/t) ln (a/a-x), where k is the rate constant of the reaction,

t is the time of the reaction

a is the initial concentration of the reactant

a-x is the remaining concentration at time (t)

a = 45.0 g the initial concentration at t = 0 year.

at t = 22 year, a-x = 22.5 g

then k = (1/22 year) ln (45.0 g/ 22.5 g) = 0.0315 year-1.

the half-life time (t1/2) = ln 2/ k = 0.693/ k =0.693/ 0.0315 = 22 years.

part 2:

using the same law k = (1/t) ln (a/a-x),

using the given data; a = 308.0 g and a-x = 4.8125 g and the calculated k from the part 1 (k = 0.0315 year-1)

t = (1/k) ln (a/a-x) = (1/0.0315) ln (308.0/ 4.8125) = 132.02 years