Chemistry Test - 13

Binding energy = 64 MeV

Binding energy/nucleon = 6.4

∴ Number of nucleon = 64/64 = 10

Main Concept :
Binding Energy Per NucleonThe binding energy per nucleon of a nucleus is the binding energy divided by the total number of nucleons.

Binding energy per Nucleon= Binding energy / Total number of nucleons.
Other Concepts :

Concept 1 :
Binding Energy Binding energy or Separation energy : Energy required to move an electron from any state to n = ∞ called binding energy of that state. or energy released during formation of an H-like atom/ion from n = ∞ some particular n is called binding energy of that state Binding energy of ground stale of H-atom = 13.6 eV.

Binding energy of Nucleus

The energy required to separate particles which are bound by electromagnetic or nuclear forces (infinitely far apart). In the case of the nucleus of an atom, these particles are protons and neutrons held together by the nuclear binding energy. The neutron and proton binding energies are the energies necessary to release a neutron or proton from the nucleus. Electron binding energy is the energy required to completely remove an electron from an atom or a molecule. The binding energy of nucleons in the nucleus of an atom amounts for most nuclei (i.e. Z>5) to around 8 MeV per nucleon. However in the case of the heaviest nuclei of an atom, such as uranium, the binding energy per nucleon is slightly less negative than for nuclei with medium mass numbers. Therefore, the fission of an uranium nucleus into two nuclei of medium mass number results in a total more negative binding energy leading to energy being released to the outside. Similarly the binding energy of the light nuclei of the hydrogen isotopes deuterium and tritium is significantly less negative than that of the helium nucleus He-4. Thus, energy is released during the fusion of deuterium and tritium to helium.

KEY CONCEPTS

Preparation of Amines
The alkylation of ammonia, Gabriel synthesis, reduction of nitriles, reduction of amides, reduction of nitrocompounds, and reductive amination of aldehydes and ketones are methods commonly used for preparing amines.

Alkylation of ammonia

The reaction of ammonia with an alkyl halide leads to the formation of a primary amine. The primary amine that is formed can also react with the alkyl halide, which leads to a disubstituted amine that can further react to form a trisubstituted amine. Therefore, the alkylation of ammonia leads to a mixture of products.

Because amides are easily prepared, their reduction is a preferred method for making all classes of amines. Reduction of nitro compounds Aromatic amines are normally prepared by reduction of the corresponding aromatic nitro compound.

Reductive amination of aldehydes and ketonesAldehydes or ketones can be reduced by catalytic or chemical reductions in the presence of ammonia or primary or secondary amines, producing primary, secondary, or tertiary amines.The reaction of a ketone with ammonia, followed by catalytic reduction or reduction by sodium cyanoborohydride, produces a 1^o amine.

Reactions of aliphatic amines with Nitrous acid

Primary amines and nitrous acid

The main observation is a burst of colourless, odourless gas. Nitrogen is given off.

Unfortunately, there is no single clear-cut equation that you can quote for this. You get lots of different organic products. For example, amongst the products you get an alcohol where the -NH₂ group has been replaced by OH. If you want a single equation, you could quote (taking 1-aminopropane as an example):

CH₃CH₂CH₂NH₂ + HNO₂ → CH₃CH₂CH₂OH + H₂O + N₂

But the propan-1-ol will be only one product among many - including propan-2-ol, propene, 1-chloropropane, 2-chloropropane and others.

The nitrogen, however, is given off in quantities exactly as suggested by the equation. By measuring the amount of nitrogen produced, you could use this reaction to work out the amount of amine present in the solution.

Secondary amines and nitrous acid

This time there isn't any gas produced. Instead, you get a yellow oil called a nitrosamine. These compounds are powerful carcinogens - avoid them!

Chloroxylenol, also known as para-chloro-meta-xylenol (PCMX), is an antiseptic and disinfectant which is used for skin disinfection and cleaning surgical instruments.

Main Concept :
Antiseptics and Disinfectants

A chemical substance which has ability to alter the normal body functions of a living organism after injection is called as drug. In medicinal chemistry, a drug can be used for the treatment of diseases caused by microorganism like bacteria, virus, fungi etc.

Generally drugs inhibit the synthesis of cell wall, or cell membrane proteins to prevent the growth of these microorganism or they can be interfere with the processing of nucleic acids of these microorganism to control them. Drugs are complex molecules containing carbon, hydrogen with some heteroatom like oxygen, nitrogen, sulphur.

On the basis of their action of different microorganism and mode of action, drugs can be various types. Some common classes of drugs are as follows.

1.  Antipyretics: These drugs used to reduce fever.

2. Analgesics: They are painkiller which used to reduce pain

3. Antimalarial drugs: These drugs use to treat malaria

4. Antibiotics: They inhibited the germ growth which caused disease

5. Antiseptics: They used to prevention of germ growth near burns, cuts and wounds

Some common natural antiseptics with their applications are as follows:

• Lemon: The presence of citrus juice in lemon make it a good antiseptic which effect on immune function system, circulatory system and digestive systems. Because of its antibacterial nature, it can use to sterilize the air by using few of its drops in a spray bottle.

• Honey: it is a natural antiseptic which used to prevent the infection of wounds due to presence of antibacterial agents which kill the bacteria present in and around the wound. It can also be used for treating ulcers and burns, diarrhea and any vomiting and stomach upsets.

• Pineapple: This fruit is rich in vitamin- A, C, and B, with manganese, which involve in metabolism of proteins and carbohydrates. Bromelain enzyme present in pineapple is used for digesting proteins and enhances medical antibiotics due to its antibacterial properties. Because of antiseptic and astringent nature of pineapple, it can used treatment of pneumonia and infection caused by worms. It is also effective in the treatment of kidney infections and kidney stones.

• Tea Tree Oil: it used for skin disinfectant like acne, athlete's foot and wound healing.

• Lavender: It is a natural antiseptic and astringent which helps with minor skin problems.

• Eucalyptus: It has antiviral and antibacterial properties, thus used for the treatment of flu, throat infections, sinusitis and headaches. Compare to natural antiseptic, synthetic antiseptics are in much more uses due to their reactivity towards bacteria.

Some common examples of synthetic antiseptics are as follow.

1. Alcohols: Some alcohols like ethanol, propanol (1-propanol, 2-propanol) and mixtures of alcohols act as good antiseptics. These alcoholic solutions commonly known as surgical alcohol and used for disinfection of skin before injection along with other antiseptics like tincture of iodine, chlorhexidine etc.

2. Quaternary ammonium compounds: These compounds can act as antibiotic as well as antiseptics also. For example; Benzethonium chloride. These compounds are commonly abbreviated as "Quats," and used to sterilize the skin before surgery as well as for irrigation or as a preservative in eye drops.

3. Boric acid: It's a white crystalline solid, chemically known as orthoboric acid (H₃BO₃). It is mainly used as suppository in the treatment of yeast infections in vagina, in eyewashes. 4. Brilliant Green: It is a triarylmethane dye used as 1% ethanol solution for treatment of small wounds and abscesses.

5. Chlorhexidine Gluconate: It is a biguanidine derivative of chlorhexidine whose alcoholic solution is widely used for skin treatment and for gingivitis.

6. Hydrogen peroxide: The 20 volume solution of hydrogen peroxide acts as good antiseptic due to its oxidising nature and used to clean wounds and ulcers. It also present in many households first aid used to cleanse wounds, disinfect skin, as a gargle or mouthwash.

7. Iodine: The alcoholic solution of iodine is known as tincture of iodine is a good antiseptic used to gentle washing of minor wounds.

8. Octenidine dihydrochloride: It is a bis-(dihydropyridinyl)-decane derivative and a cationic surfactant which show similar in their action to the Quaternary ammonium compounds, but with broader spectrum of activity.

9. Phenolic compounds: Phenol and other phenolic compounds are very common antiseptics used as an antiseptic baby powder, used in mouthwashes and throat lozenges.

10. Other antiseptics: some other antiseptics are polyhexamethylene biguanide (PHMB), Sodium chloride, Sodium hypochlorite, Calcium hypochlorite, Sodium bicarbonate (NaHCO₃) and, Terpenes.

Disinfectants:

Disinfectants are used to kill bacteria. They are used to sterilize instruments, utensils, clothes, floors, sanitary fittings, sputum and excreta. They harm the living tissues and cannot be used on skin. Some examples are phenol, methyl phenol, hydrogen peroxide and sulfur dioxide.

Hence, the number of atoms in 80 g of oxygen is equal to the number of atoms in 5 g of hydrogen.
Main Concept :
Measurements of matter in terms of molesOne mole of any substance contains a fixed number (6.022 × 10²³) of any type of particles (atoms or molecules or ions) and has a mass equal to the atomic or molecular weight, in grams. Thus it is correct to refer to a mole of helium, a mole of electrons, or a mole of Na⁺, meaning respectively Avogadro’s number of atoms, electrons or ions.

Bakelite is a thermosetting plastic formed by reaction of phenol with HCHO in the presence of conc. H₂SO₄.

It is a cross-linked polymer, condensation taking place at o- and p- positions. Thus, HCHO.

KEY CONCEPTS

Thermosetting polymers

These polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible. These cannot be reused. Some common examples are bakelite, urea-formaldelyde resins, etc.

Key Concept

Bond characteristics (i) Bond lenght, (ii) Bond angle, (iii) Bond Energy, (iv) Odd electron bonds

BOND CHARACTERISTICS

1.Bond Length: The distance between the nuclei of two atoms bonded together is termed as bond length or bond distance. It is expressed in angstrom ÅÅ units or picometer (pm).

It is thus evident that transition from 4p to 3p (Δl=0) will not give line spectrum.

Emission spectrum of hydrogen

Emission Spectrum of Hydrogen

When an electric current is passed through a glass tube that contains hydrogen gas at low pressure the tube gives off blue light. When this light is passed through a prism (as shown in the figure below), four narrow bands of bright light are observed against a black background.

​(i) Continuous spectrum : When sunlight is passed through a prism, it gets dispersed into continuous bands of different colours. If the light of an incandescent object resolved through prism or spectroscope, it also gives continuous spectrum of colours.

(ii) Line spectrum : If the radiation’s obtained by the excitation of a substance are analysed with help of a spectroscope a series of thin bright lines of specific colours are obtained. There is dark space in between two consecutive lines. This type of spectrum is called line spectrum or atomic spectrum.

(2) Absorption spectrum : Spectrum produced by the absorbed radiations is called absorption spectrum. Hydrogen spectrum

(1) Hydrogen spectrum is an example of line emission spectrum or atomic emission spectrum.

(2) When an electric discharge is passed through hydrogen gas at low pressure, a bluish light is emitted.

(3) This light shows discontinuous line spectrum of several isolated sharp lines through prism.

(4) All these lines of H-spectrum have Lyman, Balmer, Paschen, Barckett, Pfund and Humphrey series. These spectral series were named by the name of scientist discovered them.

(5) To evaluate wavelength of various H-lines Ritz introduced the following expression,

​Where R is universal constant known as Rydberg’s constant its value is 109, 678 cm^-1.

Examples on Rydberg formula

What is the wavelength of the light emitted on electron transition?

The process of electroplating a substance with a layer of Zinc is called Galvanisation.

Main Concept :
Properties of Zinc Properties of Zn : Zinc is more reactive than mercury. It a good conductor of heat and electricity. Zinc readily combines with oxygen to form ZnO. Pure zinc does not react with non-oxidising acids (HCI H₂SO₄) but the impure reacts forming Zn²⁺ ions and evolving H₂ gas.

Beryllium have higher value of IE, than boron because Be has fulfilled configuration.

Main Concept :
Ionisation potential

Ionisation potential (or ionisation energy) is the amount of energy required to remove one or more electrons from the outermost shell of an isolated gaseous atom in their ground state. Ionisation energy is also known as ionisation potential because it is measured as the minimum potential difference required to remove the ' most loosely held electrons from the rest of the atom. It is measured in eV unit per atom or kJ per mole. Following trends are observed for ionisation energy in Periodic Table :

(i) Metals usually have low ionisation energy whereas non-metals have high ionisation energies. Inert gases have maximum ionisation energy in its period.

(ii) IE increases across the period due to increased effective nuclear charge.

(iii) IE decreases down the group due to extra shells.

(iv) IE for a stable electronic configuration of half filled & fully filled subshells is abnormally high.

IE₃ > IE₂ > IE₁ for same element and relative stability of symmetrical configuration is in the order of d⁵ < p³ < d¹⁰< p⁶  1 e.V./atom = 96.49 KJ/mole = 23.06 Kcal/mole.
Variation of Ionisation enthalphy in periodic table.

The ionisation enthalpies decrease in a group from top to bottom. There is exception to the above trend after the element with atomic number 72. The ionisation enthalpy of the elements from Ta(73) to Pb(82) are higher than those of the elements of same subgroup above them. For example, Tl has higher ionisation enthalpy than In and Pb has higher value than Sn. This abnormal behaviour is due to Lanthanide contraction.

The ionisation enthalpies of inert gases are exceptionally high due to stable configurations, i.e., fully filled orbitals.

In a period, the value of ionisation enthalpy increases from left to right with breaks where the atoms have somewhat stable configurations.

Other Concepts :

Concept 1 :
Ionisation potential & Trends

The ionization potential is the minimum amount of energy required to remove one electron from each atom in a mole of atoms in the gaseous state. The first ionization energy is the energy required to remove two, the ionization energy is the energy required to remove the atom's nth electron, after the (n −1) electrons before it have been removed. Trend-wise, ionization energy tends to increase while one progresses across a period because the greater number of protons (higher nuclear charge) attract the orbiting electrons more strongly, thereby increasing the energy required to remove one of the electrons. Ionization energy and ionization potentials are completely different. The potential is an intensive property and it is measured by "volt" ; whereas the energy is an extensive property expressed by "eV" or "kJ/mole".

As one progresses down a group on the periodic table, the ionization energy will likely decrease since the valence electrons are farther away from the nucleus and experience a weaker attraction to the nucleus's positive charge. There will be an increase of ionization energy from left to right of a given period and a decrease from top to bottom. As a rule, it requires far less energy to remove an outer-shell electron than an inner-shell electron. As a result, the ionization energies for a given element will increase steadily within a given shell, and when starting on the next shell down will show a drastic jump in ionization energy. Simply put, the lower the principal quantum number, the higher the ionization energy for the electrons within that shell. The exceptions are the elements in the boron and oxygen family, which require slightly less energy than the general trend. Helium has the highest ionization energy while Francium has the lowest.

Factor Influencing Ionization energy
Variation in ionization energies in a period and group may or may not be regular and can be influenced by the following factor.
(A)Size of the Atom :
lonisation energy decreases with increase in atomic size.
As the distance between the outer most electrons and the nucleus increases, the force of attraction between the valence shell electrons and the nucleus decreases. As a result, outer most electrons are held less firmly and a lesser amount of energy is required to knock them out.
For example, ionization energy decreases in a group from top to bottom with an increase in atomic size.
 
(B)Magnitude of Nuclear Charge :
lonisation energy increases with an increase in nuclear charge. This is due to the fact that with an increase in nuclear charge, the electrons of the outer most shell are more firmly held by the nucleus and thus greater amount of energy is required to pull out an electron from the atom.
For example, ionization energy increases as we move from left to right along a period due to the increase in nuclear charge.

(C)Shielding or screening effect :
The inner electronic shells act as a screen between the nucleus and the outer shell. This reduces the inward pull of the outer shell towards the nucleus. In other words, the electrons that lie between the nucleus and the valence (i.e. outermost) shell have a shielding or screening effect on the electrons of valence (i.e. outermost) shell. This is called the shielding effect. The larger the number of electrons in the inner shells, the greater will be the screening effect and lesser will be the nuclear attraction of the outermost electrons. Thus increase in the number of inner electrons will tend to decrease ionization energy. It should be carefully noted that electrons in the same or similar type of orbital do not shield each other. Thus the electrons in s-orbital will not shield each other. Similaly, electrons in p_x, p_y and p_z orbital of the same subshell do not shield each other. It has also been found that the screening effect of
s-electrons is more than that of p-electron shoes effect is in turn more than that of a d-electron and so on.

(D)Penetration effect of the electron :
The ionization energy also depends on the type of electron which is removed. s, p, d and f electrons  have orbitals with different shapes. An s electron penetrates close to the nucleus, and is therefore more tightly held than a p electron. Similarly a p-orbital electron is more tightly held than a d-orbital electron and a d-orbital electron is more tightly held than an f-orbital electron. All other factors being equal, ionization energies are in the order s>p>d>f .
 For example, the ionization energy of aluminium is comparatively less than magnesium because the outer most electron is to be removed from a 3p-orbital (having lesser penetration effect) in aluminium where as in magnesium it will be removed from a 3s-orbital (having larger penetration effect) of the same energy level.

(E)Electronic Configuration :
If an atom has exactly half-filled or completely filled orbitals, then such an arrangement has extra stability.
The removal of an electron from such an atom requires more energy then expected. For example, the first ionization energy of beryllium is greater than boron because beryllium has an extra stable completely filled outer most 2s orbital while boron has a partially filled less stable outer most 2p-orbital.

Iodoform test is given by only those compounds containing CH₃CO – or CH₃CHOH – group.

KEY CONCEPTS

Nucleophilic addition reactions of Aldehydes and Ketones
Aldehydes and ketones undergo a variety of reactions that lead to many different products. The most common reactions are nucleophilic addition reactions, which lead to the formation of alcohols, alkenes, diols, cyanohydrins (RCH(OH)C = N), and imines R₂C = NR → ), to mention a few representative examples.

Addition of water

The addition of water to an aldehyde results in the formation of a hydrate.

The formation of a hydrate proceeds via a nucleophilic addition mechanism.

I. Water, acting as a nucleophile, is attracted to the partially positive carbon of the carbonyl group, generating an oxonium ion.

II. The oxonium ion liberates a hydrogen ion that is picked up by the oxygen anion in an acid‐base reaction.

Addition of alcohol

Reactions of aldehydes with alcohols produce either hemiacetals (a functional group consisting of one --OH group and one --OR group bonded to the same carbon) or acetals (a functional group consisting of two --OR groups bonded to the same carbon), depending upon conditions. Mixing the two reactants together produces the hemiacetal. Mixing the two reactants with hydrochloric acid produces an acetal. For example, the reaction of methanol with ethanal produces the following results:

A nucleophilic substitution of an OH group for the double bond of the carbonyl group forms the hemiacetal through the following mechanism:

I. An unshared electron pair on the alcohol's oxygen atom attacks the carbonyl group.

II. The loss of a hydrogen ion to the oxygen anion stabilizes the oxonium ion formed in Step I.

Oximes, 2, 4‐dinitrophenylhydrazones, and semicarbazones are often used in qualitative organic chemistry as derivatives for aldehydes and ketones.

Haloform reactions of aldehydes and ketones

The Haloform Reaction

Methyl ketones typically undergo halogenation three times to give a trihalo ketone due to the increased reactivity of the halogenated product as discussed above. This trihalomethyl group is an effective leaving group due to the three electron withdrawing halogens and can be cleaved by a hydroxide anion to effect the haloform reaction. The product of this reaction is a carboxylate and a haloform molecule (CHCl₃, CHBr₃, CHI₃). Overall the haloform reaction represents an effective method for the conversion of methyl ketones to carboxylic acids. Typically, this reaction is performed using iodine because the subsequent iodoform (CHI₃) is a bright yellow solid which is easily filtered off.