discuss the solubility differences between the halogens and the halides in both hexane and water. be sure to define what a halogen and halide are to foundation your discussion.
James
Guys, does anyone know the answer?
get discuss the solubility differences between the halogens and the halides in both hexane and water. be sure to define what a halogen and halide are to foundation your discussion. from EN Bilgi.
Background
Background
One of the most useful things about studying chemistry is discovering the amount of useful information contained in the periodic table. Many of these periodic properties of the elements are discussed in your textbook.
In today’s experiment, some of the properties of the Group 7A (Group 17) elements, known as halogens, and their compounds will be explored. The solubility properties of the halogens will be used to observe their reactions.
The more electronegative an element is, the more it attracts electrons. Group 17 atoms that have become ions by gaining an extra electron, such as F–, Cl–, Br–, and I–, are called halides. Note that the chlorine atom in NaCl, sodium chloride, is a halide—specifically a chloride. Also note that anions such as halides must always be paired with cations when found in the formula for a binary ionic compound. Group 17 atoms in their natural diatomic state, such as F2, Cl2, Br2, and I2, are called halogens. In this experiment, the relative electronegativities of the halogens will be determined.
If a solution containing halide, X–, is added to a solution of a different halogen, Y2, there are two possibilities. When element Y is more electronegative than element X, Y2 will take the electron from X–, leaving X2 as a halogen. On the other hand, when Y2 is less electronegative than X–, no reaction will take place, and Y2 remains as the halogen. In terms of balanced equations:
The properties of two solvents, water and hexane, will be useful in sorting out what happens in this type of reaction. Water is a polar solvent and it will solvate polar species whether they are ionic or molecular. This means that a polar molecule (one that has a dipole moment) or an ionic compound may dissolve in water. A diatomic molecule is polar if the two atoms have different electronegativities. Identify which of the halogens and halides in the above equations are ionic and which are non-ionic.
Non-polar solvents solvate non-polar molecules. Hexane is an organic molecule that is non-polar. Since water is polar and hexane is non-polar, the two do not mix. When combined, two distinct, colorless layers are formed with water, the denser liquid, on the bottom.
If colored substances are added to a test tube containing water and hexane, the polarity of the compounds can be determined. If they are non-polar, they will color the hexane layer. If the colored substances are polar, the color is observed in the water layer.
For the first reaction described above, if Y2 is green before any reaction takes place, the hexane layer is green because non-polar compounds will reside in the hexane layer. As the reaction proceeds, the green disappears from the hexane layer because the Y2 molecules are reacting and disappearing. The hexane will then take on the color of X2. In the second case, where X is more electronegative than Y, the more electronegative atom already has the electrons, so no reaction will occur. Since no reaction occurs, the hexane layer will remain green, the color of Y2.
Whenever a color change occurs, this is a clue that a reaction is taking place. Three halogens in aqueous (water) solutions will be available: chlorine, bromine and iodine. Each of these halogens has a distinctly different color in hexane. Therefore, by observing the color of the hexane layer, the halogen present can be determined.
Solved 1. Discuss the solubility differences between the
Answer to Solved 1. Discuss the solubility differences between the
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Atomic and Physical Properties of Halogens
Atomic and Physical Properties of Halogens
Last updated Aug 21, 2020
Group 17: Physical Properties of the Halogens
Group 17: General Properties of Halogens
Donate Jim Clark
Truro School in Cornwall
This page discusses the trends in the atomic and physical properties of the Group 7 elements (the halogens): fluorine, chlorine, bromine and iodine. Sections below cover the trends in atomic radius, electronegativity, electron affinity, melting and boiling points, and solubility, including a discussion of the bond enthalpies of halogen-halogen and hydrogen-halogen bonds.
Trends in Atomic Radius
The figure above shows the increase in atomic radius down the group.
Explaining the increase in atomic radius
The radius of an atom is determined by:
the number of layers of electrons around the nucleus
the pull the outer electrons feel from the nucleus.
Compare the numbers of electrons in each layer of fluorine and chlorine:
F 2,7 Cl 2,8,7
In each case, the outer electrons feel a net +7 charge from the nucleus. The positive charge on the nucleus is neutralized by the negative inner electrons.
This is true for all the atoms in Group 7: the outer electrons experience a net charge of +7..
The only factor affecting the size of the atom is therefore the number of layers of inner electrons surrounding the atom. More layers take up more space due to electron repulsion, so atoms increase in size down the group.
Trends in Electronegativity
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. It is usually measured on the Pauling scale, on which the most electronegative element (fluorine) is assigned an electronegativity of 4.0. The figure below shows electronegativities for each halogen:
Notice that electronegativity decreases down the group. The atoms become less effective at attracting bonding pairs of electrons. This effect is illustrated below using simple dots-and-crosses diagrams for hydrogen fluoride and hydrogen chloride:
The bonding pair of electrons between the hydrogen and the halogen experiences the same net pull of +7 from both the fluorine and the chlorine. However, in the chlorine case, the nucleus is farther away from the bonding electrons, which are therefore not as strongly attracted as in the fluorine case.
The stronger attraction from the closer fluorine nucleus makes fluorine more electronegative than chlorine.
Summarizing the trend down the Group
As the halogen atoms increase in size, any bonding pair gets farther away from the halogen nucleus, and so is less strongly attracted toward it. Hence, down the group, the elements become less electronegative.
Trends in First Electron Affinity
The first electron affinity is the energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous 1- ions. In other words, it is the energy released in the following process:
X(g)+ e − → X − (g) (1) (1)X(g)+e−→X−(g)
First electron affinities have negative values by convention. For example, the first electron affinity of chlorine is -349 kJ mol-1. The negative sign indicates a release of energy.
The first electron affinities of the Group 7 elements
The electron affinity is a measure of the attraction between the incoming electron and the nucleus. There is a positive correlation between attraction and electron affinity. The trend down the group is illustrated below:
Notice that the trend down the group is inconsistent. The electron affinities generally decrease (meaning less heat is emitted), but the fluorine value deviates from this trend.
In the larger atom, the attraction from the more positive nucleus is offset by the additional screening electrons, so each incoming electron feels the effect of a net +7 charge from the center.
As the atom increases in size, the incoming electron is farther from the nucleus and so feels less attraction. The electron affinity therefore decreases down the group. However fluorine is a very small atom, with the incoming electron relatively close to the nucleus, and yet the electron affinity is smaller than expected.
Another effect must be considered in the case of fluorine. As the new electron comes approaches the atom, it enters a region of space already very negatively charged because of the existing electrons. The resulting repulsion from these electrons offsets some of the attraction from the nucleus.
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