Chemistry Test-8

The structural formula of Haloalkane is R-X.

• It was derived from alkanes containing a halogens or more.
• They are used as flame retardants, fire extinguishers, refrigerants, propellants, solvents, and medicinal items.
• "RX" in which R is an alkyl or alkyl substituted group and X is a halogen (F, Cl, Br, I).
• Haloalkanes are commonly used in organic synthesis as synthonous alternatives to alkyl cation (R+).

C₄H₉ is not a homologous series.

Homologous series:

• ​Homologous series is a series of compounds with similar chemical properties and some functional groups differing from the successive member by CH₂.
• Carbon chains of varying length have been observed in organic compounds having the same general formula.
• Alkanes with general formula C_nH_2n+2, alkenes with general formula C_nH_2n and alkynes with general formula C_nH_2n-2 form the most basic homologous series in organic chemistry.

Carbon has the unique ability to form bonds with other atoms of the same element giving rise to large molecules.

• ​The elements in the periodic table show certain properties owing to their nature and size.
• Catenation is the unique ability of an element to form bonds with other atoms of the same element giving rise to large molecules.
• Carbon is the only element that shows the property of catenation to a very high extent.
• Owing to its small size, carbon can form long carbon-carbon chains with stable bonds.
• The tetravalency of carbon allows it to bond to four other atoms simultaneously. This tendency helps carbon in the forming branched and ring structures.

AgCl, AgBr and AgI are used in photography.

Silver halides are used in black and white photography.

A photographic film is coated with silver halide. When light falls on the surface, the exposed part of the film is darkened from which photograph is developed. That’s why it is used in photography.

The salts are reduced to the metal form when light falls on them.

• \(\mathrm{AgCl}+\mathrm{hv} \rightarrow \mathrm{Ag}^{+}+\mathrm{Cl}+1\) electron
• \(\mathrm{Ag}^{+}+1 \mathrm{e}^{-} \rightarrow \mathrm{Ag}\)

When silver metal is formed, it forms a dark image on the film.

When we take a picture, the camera lens projects a small but accurate image on the surface of this light-sensitive layer, and the silver bromide is decomposed more or less, depending on the intensity of the light received in various points of the image.

So, silver halides for its unusual sensitivity to light are used in photography.

Glycerol is a chemical compound, generally nontoxic, sweet-tasting viscous liquid with the chemical formula C₃H₈O₃.

• It possesses the property of humectant - a substance that attracts water.
• It can draw in moisture, preventing drying of the skin.
• Hence, Glycerol is added to soap to prevent rapid drying.
• Soaps used for cleaning purposes are sodium or potassium salts of long-chain fatty acids, e.g., stearic, oleic, and palmitic acids.
• Soaps containing sodium salts are formed by heating fat (i.e., glyceryl ester of fatty acid) with aqueous sodium hydroxide solution.
• This reaction is known as Saponification.

The above mentioned reagents are used for conducting hydroboration-oxidation. Hydroboration oxidation follows the following mechanism(For Propene):

From the figure, it is evident that the product is propan-1-ol. The hydroboration-oxidation mechanism produces anti-Markonikoff addition of water molecules across the double bond.

Osmosis: The net spontaneous flow of the solvent molecules from the solvent to the solution or from a less concentrated solution to a more concentrated solution through a semi-permeable membrane is called osmosis.

Osmotic pressure: The external pressure that must be applied to the solution side to stop the passage of solvent into the solution through a semi-permeable membrane is known as osmotic pressure.

The osmotic pressure method has the advantage over other method as pressure measurement is around the room temperature and molarity of the solution is used instead of molarity. As compare to other colligative properties, its magnitude is large even for every dilute solution. Therefore molar mass can be determined by it.

The figure shows a simple osmotic cell. Both compartments contain water, but the one on the left also contains a solute whose molecules (represented by blue circles) are too large to pass through the membrane. Many artificial and natural substances are capable of acting as semi-permeable membranes. The walls of most plant and animal cells fall into this category.

Silver Bromide is used in black and white photography.

A photographic film is coated with silver bromide. when light falls on the surface, the exposed part of the film is darkened from which photograph is developed. That’s why it is used in photography.

When we take a picture, the camera lens projects a small but accurate image on the surface of this light-sensitive layer, and the silver bromide is decomposed more or less, depending on the intensity of the light received in various points of the image.

Silver bromide (AgBr), a soft, pale-yellow, water-insoluble salt well known (along with other silver halides) for its unusual sensitivity to light.

Formaldehyde is also known as formalin.

It is an organic compound which occurs naturally with formula CH₂O (H−CHO).

It is an effective precursor for many other chemicals and compounds.

This is primarily used in industrial resin processing, e.g. for particle boards and coatings.

Acetaldehyde and Acrolein are the Aldehydes while Acetone is the Ketones.

Halogens have a strong tendency to accept electrons.

Halogens accept electrons from other metals and become uni negative.

The other substance is oxidized.

The substances that accept electrons from others are termed as oxidizing agents. Thus, halogens act as good oxidizing agents.

The oxidizing powers of halogens are measured in terms of their electrode potentials.

The electrode potentials of halogens decrease in the order:

\(\mathrm{F}_{2}(+2.87 \mathrm{~V})>\mathrm{Cl}_{2}(+1.36 \mathrm{~V})>\mathrm{Br}_{2}(+1.09 \mathrm{~V})>\mathrm{I}_{2}(+0.54 \mathrm{~V})\)

Higher electrode potential means a stronger oxidizing agent.

Thus, the decreasing order of oxidizing power of halogens is F > Cl > Br > I.

Transition elements are those elements whose two outermost shells are incomplete.

These elements have partially filled d-subshell in the ground state or any of their common oxidation state and are commonly referred to as d-block transition elements.

The generalized electronic configuration of these elements is (n-1) d^1–10 ns^1–2.

The d-block elements are categorized as 1st series transition elements, 2nd series transition elements, 3rd series transition elements and 4th series transition elements.

The examples are: Cu, Zn, Ag, Cd, Au, Hg, etc.

The required transition is \(n_{1}=2\) to \(n_{2}=\infty\) and corresponding transition energy is:

\(\Delta E=21.7 \times 10^{-12}\left(\frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}}\right) \mathrm{erg}\)

\(=\frac{21.7}{4} \times 10^{-12} \mathrm{erg}\)

\(=5.425 \times 10^{-12} \mathrm{erg}\)

The longest wavelength that can cause the above transition can be determined as:

\(\lambda=\frac{h c}{\Delta E}=\frac{6.625 \times 10^{-34} \times 3 \times 10^{8}}{5.425 \times 10^{-12} \times 10^{-7}}\)

\(=3.66 \times 10^{-7} \mathrm{~m}=3.6 \times 10^{-5} \mathrm{~cm}\)

Bohr proposed an idea of stationary orbits in which electron revolves. According to Bohr's electron does not lose energy as long as it stays in a stationary orbit. When an electron jumps to lower stationary orbit, energy is lost in the form of electromagnetic radiation. Conversely, when energy is supplied, the electron jumps to a higher stationary orbit.

Sublimation is a change in a state of matter, just like melting, freezing, and evaporation. Through sublimation, a substance changes from a solid to a gas without ever passing through a liquid phase.

Example: Dry ice, solid CO₂, Naphthalene.

Evaporation: Evaporation is the process by which water changes from a liquid to a gas or vapor.

Distillation: Distillation is the process of separating components of a mixture based on different boiling points. Examples of uses of distillation include

• purification of alcohol desalination
• crude oil refining
• making liquefied gases from the air

Crystallization: Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal.