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Describe how the rate of movement of a substance compared to the rate of movement of the solvent can be used to identify a substance in a chromatography experiment?
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What is chalk chromatography?
In 1906, Mikhail Tswett, a Russian botanist, published a paper in which he described the separation of pigments, extracted from green leaves, by washing the mixture with petroleum ether (similar to lighter fluid) through a glass tube packed with powdered calcium carbonate (chalk). As the mixture of pigments passed down the CaCO3 -filled tube, they separated into distinctly colored zones. Tswett gave the name chromatography (the graphing of colors) to this separation technique. The method that Tswett used is known today as column chromatography. Column chromatography is a rather slow and sometimes difficult process to carry out compared with more recent developments known as paper chromatography, thin layer chromatography, gas chromatography, high pressure liquid chromatography, and ion chromatography. The method of column chromatography can be carried out in the classroom using calcium carbonate in the form of sticks of chalk. A mixture containing two or more components is deposited on a stick of chalk, a solid adsorbing substance. The components are adsorbed (i.e., held on the surface of the solid substance) to varying degrees which depend on the nature of the component, the nature of the adsorbant, and the temperature. Then the wash solvent (liquid) is added to the adsorbant and allowed to flow through it by capillary effect. As the solvent passes the deposited mixture, the components tend to be dissolved to varying extents and are swept along the solid adsorbant. The rate at which a component will move along the solid depends on its relative tendency to be dissolved in the solvent and its tendency to be adsorbed on the solid. The net effect is that, as the solvent passes slowly through the solid adsorbant, the components of the mixture -separate from each other and move along with the solvent forming rather diffuse zones or spots. With the proper choice of solvent and adsorbant, it is possible to resolve many complex mixtures into their components.
What defines the ratio of the density of a substance compared to the density of water at 4 celsius?
specific gravity
How can proteins be analyzed by chromatography?
A solution of amino acids is spotted onto a piece of chromatography paper which is then placed into a container filled with a suitable solvent. A dye is used so that the position of the amino acids along the piece of paper can be seen. The distances travelled by the amino acids are measured to calculate their retention factors (Rf) values. These are then compared to known standards.
Describe the roles of a catalyst and substrate in a chemical reaction?
A catalyst is a substance that speeds up the rate of a chemical reaction. Catalysts work by lowering a reaction's activation energy.A substrate is a reactant of an enzyme-catalyzed reaction.
Which dye would be more soluble in n-propyl alcohol the blue of the yellow?
Paper chromatography separates compounds based on their. A polar molecule has one end that is more positively charged than the other end. Blue dye is more polar compared to red.
Why are controls not needed in the arthropods experiment describe in the study guide?
The treatments can be compared to each other instead of to a control
In an experiment what is the experimental data compared to?
In an experiment there is one thing that it is compared with experimental data. This is when the end results.The experiment data is compared to one thing. It is compared to the end results.
How you might use Rf values to identify an unknown substance?
Although Rf values technically remain constant if the following are held constant: * solvent system * adsorbent * thickness of the adsorbent * amount of material spotted * temperature They are generally not used to identify an unknown substance specifically, since these factors are sometimes difficult to control. Most generally, during a chromatography experiment an unknown sample can be compared directly to a known sample simultaneously, i.e. they will have similar Rf values.
What is the name for an experiment in which a controlled group is compared with an experimental group?
A controlled experiment
What is the standard that an experiment's results be compared?
Data :)
What is the standard that results are compared to in an experiment?
Control
What is the standard to which an experiment can be compared?
it is called the control
What happens in an controlled experiment?
the two groups are compared
What is the standard to which an experiment's results can be compared?
it is called the control
When you sum up what is learned in an experiment what is it called?
The outcome of an experiment is a "conclusion", the interpretation of the results compared with the expected results and the goal of the experiment.
What is the retardation factor?
In chemical chromatography, it is a measure of the relative mobility of components of a mixture through a stationary phase while experiencing the forces of a mobile eluent phase, based on relative intermolecular attractive forces and molecular size. In thin layer chromatography, is it the ratio of distance travelled by a component compared to the distance travelled by the eluent front from the point of contact with the mixture. In column chromatography, it is the fraction of the component in the mobile phase at equilibrium. By comparison, in gas chromatography, relative retention times on the stationary phase are measured and compared for the mixture components.
How can a substance flow?
A substance can flow if its molecules are loosely packed when compared to a solid.
