Chemistry Test-5

The process used to separate coloured components of a mixture is known as Chromatography.

Chromatography is the most widely used separation method in chemical laboratories, where it is used in research, isolation and purification, and is generally used as a part of small- and large-scale development in the chemical process industry.

Distillation is the process of using selective boiling and condensation to isolate the components or substances from a liquid mixture.

Sublimation is the transition of a material directly from the solid to the gas state, without the liquid state passing through.

Crystallization is the process through which solid forms are formed, in which atoms or molecules are highly organized into a structure known as a crystal.

1. The atoms of an element having the same atomic number but a different mass number are called isotopes.

2. The nuclei which have the same mass number but a different atomic number are called isobars.

Isotopes:

• Isotopes are those elements that have the same atomic no. but different mass no.
• The mass number is the sum total of protons and neutrons.
• For example, \({}_6^{12} \mathrm{C}, {}_6^{13} \mathrm{C}, {}_6^{14} \mathrm{C}\)
• Other examples are Hydrogen isotopes named Protium, deuterium, and tritium having mass numbers 1,2,3 respectively.
• In order to identify isotopes, one must use methods to determine the mass number.

Isobars:

• The nuclei which have the same mass number (A) but a different atomic number (Z) are called isobars.
• Examples of Isobars are \({ }^{14} \mathrm{C}_{6},{ }^{14} \mathrm{~N}_{7}\)
• From above it is clear that the nuclei which have the same mass number (A) but a different atomic number (Z) are called isobars.
• Isobars occupy different positions in the periodic table so all isobars have different chemical properties, but the same physical properties.

The adsorption of gases on solid surface is exothermic because the entropy decreases.

'It is a better electric conductor than graphite' is not true for the form of carbon known as a diamond.

Graphite has sp² hybridization of carbon and has a free electron which makes more conjugation.Diamond has sp³ hybridization of carbon and has no free electrons, hence lesser conjugation.

• Delocalization helps to make graphite stronger compared to diamonds.
• This makes graphite thermodynamically more stable as compared to diamond.
• As a result of the free electron, graphite, though a non-metal, is able to conduct electricity while diamond cannot.
• Diamond is a poor conductor of electricity but is a good conductor of heat while Graphite is a good conductor of heat and electricity.

Amides can be converted to amines by the reaction named Hoffman.

• The Hofmann reaction is an organic reaction used to convert a primary amide to a primary amine.
• In the Hofmann reaction, an amide is treated with bromine and base (usually NaOH or KOH).
• Upon heating, an intermediate isocyanate is formed, which is not isolated.
• In the presence of water, the isocyanate loses carbon dioxide to give an amine.

Perkin: A reaction used to convert an aromatic aldehyde and an anhydride to alpha - beta-unsaturated carboxylic acid.

Claisen: A reaction used to form a carbon-carbon bond between two ester molecules using an alkoxide base in alcohol to make a β-keto ester.

Clemmensen: A reaction used to reduce an aldehyde or ketone to an alkane using amalgamated zinc and hydrochloric acid.

In Victor Mayer's Test, the primary alcohols gives a characteristic color, which is red.

Victor Mayer's test:

Victor Mayer's test is performed to distinguish between the primary, secondary and tertiary alcohols. All three alcohols respond differently towards the test.

In this test, the alcohol under examination is treated as follows:

• It is treated with red phosphorus and iodine when the hydroxyl group is replaced by iodine to form the corresponding iodide.
• The iodide is then treated with silver nitrite to get the corresponding nitroalkane.
• In the last step the solution is made alkaline .
• Primary alcohols forms nitrolic acid, which on treatment with alkali gives gives blood red colouration.
• Secondary alcohols form pseudo nitrols which on treatment with alkali forms blue color solution.
• Tertiary alcohols do not produce any color change.

Lipase enzyme is produced in small amounts by mouth and stomach, and in larger amounts by the pancreas. This enzyme is responsible for the breakdown of fats into fatty acids and glycerol.

It performs essential roles in the digestion, transport, and processing of dietary lipids such as triglycerides, fats, and oils.

Amylase is secreted by the salivary glands and the pancreas.

It is essential for the digestion of carbohydrates.

Maltase is secreted by the small intestine.

It is responsible for the breakdown of maltose into glucose that the body uses for energy.

Sucrase is secreted by the small intestine where it breaks down sucrose into fructose and glucose.

Vanilla is an olfactory indicator.

Olfactory indicator is used to identify the base and acid property of the solution. When an olfactory indicator is mixed with acid or base then the smell of olfactory indicator changes.

Examples are Onion, clove oil, and vanilla.

Litmus paper is a natural indicator.

Phenolphthalein is used as an indicator of acid and base in a titration.

Red cabbage juice is also an indicator.

Oxygen gas is easily produced at a faster rate by heating a mixture of Potassium Chlorate and Manganese dioxide than heating Potassium chlorate alone, so statement I is true.

When Potassium chlorate (KClO₃) is heated in the presence of a Manganese dioxide catalyst, it breaks down and form Potassium chloride and oxygen gas.

• \(\mathrm{KClO}_{3} \stackrel{\mathrm{MnO}{}_2}{\longrightarrow} 2 \mathrm{KCl}+3 \mathrm{O}_{2}\)
• Oxygen gas is easily produced at a faster rate in the above reaction than heating Potassium chlorate alone.
• Manganese dioxide will act as a positive catalyst here.
• A catalyst is a substance that causes an increase in the rate of a chemical reaction without being used up in the reaction.
• If catalyst increases the rate of a reaction then the catalyst is known as the positive catalyst.

Manganese dioxide acts as a positive catalyst, so statement II is false.

An alkene was treated with ozone and the resulting compound on hydrolysis gave 2-pentanone and ethanal. The alkene is '3-methyl-2-hexene'.

Ozonolysis reaction:

• When ozone is passed into a solution of an alkene in presence of an inert solvent such as CCl₄; ozonolysis takes place.
• The reaction occurs at very low temperatures such as -78°C.
• The mechanism is concerted cycloaddition.
• The first step is the addition of ozone to the alkene to form an ozonide.
• Ozonides are very unstable and hence cleaved directly with reductive or oxidative conditions to produce carbonyl compounds.
• The general mechanism is:

When 3-methyl-2-hexene reacts with ozone followed by treatment with Zn and H₂​O, it will form 2-pentanone and ethanal.

Thus ozonolysis of 3-methyl-2-hexene gives 2-pentanone and ethanal.

The structural formula of this alkene is:

\(\mathrm{CH}_{3}-\mathrm{CH}=\underset{\underset{\mathrm{CH}_{3}}{|}}{\mathrm{C}}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\)

So, the alkene is 3-methyl-2-hexene.

Melamine is an example of the thermosetting plastic.

Melamine is a polymer that is composed of melamine and formaldehyde sub-units. It is also known as a melamine-formaldehyde polymer. Melamine resins are highly durable, heat and fire-resistant. Melamine is used to make kitchen utensils, floor tiles and particle boards. It is also used as a fire retardant and is added to paints.

Thermosetting plastics:

• The thermosetting plastics are the polymers which once hardened after moulding cannot be melted again to remould it.
• These polymers are formed by the cross-linking of the polymer chains and hence can not be reversed.
• These polymers have a high melting point and hence they are durable and heat resistant.

Thermoplastic polymer:

• Another kind of polymer which can be remelted and recycled is called a thermoplastic polymer.
• There is no cross-linking in these polymers and hence they can be reversed after hardening also.
• Polythene, Polyvinyl Chloride (PVC) and Polyethylene terephthalate (PET) are examples of Thermoplastic polymers.
• They can be recycled many times till their chain length is not harmed.

Acid rain: Acid rain is a by-product of a variety of human activities that emit the oxides of sulphur and nitrogen in the atmosphere.

Burning of fossil fuels (which contain sulphur and nitrogenous matter) such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides. SO₂ and NO₂ after oxidation and reaction with water are major contributors to acid rain.

2SO₂ (g) + O₂ (g) + 2H₂O (l) → 2H2SO₄ (aq)

4NO₂ (g) + O₂ (g) + 2H₂O (l) → 4HNO₃ (aq)

So, the correct option is HNO₃.

The chalcogens (ore forming) are the chemical elements in group 16 of the periodic table.

• This group is also known as the oxygen family.
• It consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive element polonium (Po).
• These elements contain six electrons in their outer shell. The general electronic configuration is ns² np⁴.
• Among the Group 16 elements, polonium is a metalloid, all the others are nonmetals. ​
• All of the chalcogens have six valence electrons, leaving them two electrons short of a full outer shell.
• Their most common oxidation states are -2, +2, +4, and +6.
• They have relatively low atomic radii, especially the lighter ones.

The particle required to continue the chain process of Uranium fission is Neutron.

Nuclear Fusion:

• When two or more light nuclei combined together to form a heavier nucleus, tremendous energy is released.
• Uncontrolled nuclear fusion results in hydrogen bombs.

Neutron:

• A neutron was discovered by James Chadwick.
• The charge on neutron is zero.
• A neutron is obtained from the radioactivity phenomenon.
• It has zero charges and mass equal to 1.674 × 10^-27 kg or 1.00867 u.
• It is present inside the nucleus. Its antiparticle is antineutrino.

Carboxylic group is present in Methanoic acid.

Carboxyl group:

• It is defined as carbonyl and hydroxyl attached to a carbon atom, which means the carbon atom is double-bonded with oxygen and a single bond with the hydroxyl.
• And Carboxylic acid is an organic compound that consists of a carboxyl group.
• The general formula of the class is R-C(O)OH.
• In this formula, R is the alkyl or aryl group.
• Carboxylic acids occur widely in nature.
• However, the majority of the members of this group are manufactured synthetically.
• The double bond presents in the structure of carboxylic acids play a very important role in the properties of the different compounds of carboxylic acids.
• When a carbon compound is attached to the functional group −COOH (carboxyl group) then the compound refers to as carboxylic acids.
• The above structure formula of methanoic acid is HCOOH, hence it contains a carboxylic acid group.