Chemistry: CUET Mock Test - 3 - CUET MCQ

In one-dimensional close packing, the constituent particles are assumed to be arranged in a row. Thus, each constituent particle comes in contact with 2 of its neighbors and thereby giving the coordination number 2.

In a two-dimensional square close packed structure, each sphere is in contact with 4 of its adjacent spheres. Hence, it has coordination number 4.

Two-dimensional hexagonal close packed structure are formed when one row of a one-dimensional structure is placed below another in such a way that spheres of second row fit in the depressions of the first row and thereby creating triangular voids between them.

Metalloids have properties intermediate to those of metals and non-metals. They are non-malleable, non-ductile and brittle. They are poor conductors of heat and electricity as compared to metals, but are better conductors than non-metals.

For any process, the change in Gibbs free energy (ΔG) is given by the equation,
ΔG = ΔH – TΔS
Where ΔH is the enthalpy change, ΔS is the entropy change and T is the absolute temperature.

The impurities generally present in crude metals consist of other metals, formed by reduction of their respective oxides present in the ore, non-metals such as silicon and phosphorus, unreacted oxides and sulphides of the metals and substances taken up in the furnace such as slag.

Group 16 of the periodic table consists of five elements viz., Oxygen (O), Sulphur (S), Selenium (Se), Tellurium (Te) and Polonium (Po). The elements of this group are commonly known as the oxygen family after the name of its first member.

Of all the halogens, fluorine is the most reactive and hence is also called super halogen. Fluorine is also the most electronegative (EN = 4.0) element in the periodic table. This indicates that fluorine has a high tendency to gain electrons from other elements with lower electronegativities.

The criterion of the feasibility of a reaction at any temperature is that the ΔG of the reaction must be negative. For a reaction to be spontaneous, the value of the change in Gibbs energy of the reaction must always be negative.

The correct option is D Tin
Distillation process is used for refining metals that are usually volatile in nature i.e. they have low boiling points. Zinc, cadmium and mercury are refined via distillation where the pure metal distills over leaving behind the non-volatile impurities.
Tin is refined via liquation process since it is a low melting metal.

Oxygen is the most abundant of all elements. It occurs in the free state as dioxygen (O₂) and makes up 20.46% by volume and 23% by mass of the atmosphere. It also occurs in the form of ozone (O₃).

Astatine (Atomic No. = 85, Symbol-At) is radioactive and hence occurs in nature only in traces. Therefore, not much is known about its chemistry, though it might be expected to be a metalloid.

A reaction with ΔG positive can still be made to occur by coupling it with another reaction having large negative ΔG so that the net ΔG of the two reactions is negative (ΔG = change in the Gibbs energy of the reaction).

A metallic crystal has valence electrons in the valence band and free moving, delocalized electrons in the conduction band. For a metal, these two bands are very close to each other.

Metallic bonds are formed between positive metal ions and the sea of delocalized electrons. This bond is stronger than covalent and ionic bonds. Due to the mobility of electrons, conduction of heat and electricity is feasible.

Semiconductors have completely filled valence bands and completely empty conduction bands. The energy gap between the two bands is relatively small and can be overcome by supplying heat, which excites some electrons to the conduction band, thus allowing the conduction of electricity.

Ellingham diagram normally consists of plots of ΔfG° vs T for formation of oxides of elements. Similar diagrams can also be constructed for sulphides and halides of elements. These diagrams help us in predicting the feasibility of thermal reduction of an ore.

Liquation is used for purification of metals that contain impurities which are less fusible than the metals themselves, that is, the melting points of the metals are lower than that of the impurities. Lead is refined by liquation process.

Penicillin is an antibacterial compound derived from Penicillium. It has a bactericidal effect on microbes. Ampicillin is a modified version of penicillin with a wider spectrum. Arsphenamine is an -As=As- linkage compound that resists bacterial action and is also toxic to human beings. Sulphanilamide is an active antibiotic compound formed in the body.

Dysidazirine is effective in treatment of only certain strains of tumour cells, hence they are narrow spectrum. Chloramphenicol, vancomycin and amoxycillin are examples of broad-spectrum antibiotics, that are used for treating different types of problems.

Dettol, tincture of iodine and iodoform are common antiseptics that are directly applied on wounds to treat them. Boric acid is prepared as a dilute aqueous solution and acts as an antiseptic for the eyes.

The band theory assumes that atomic orbitals of the atoms of the crystal combine to form molecular orbitals which are spread over the whole crystal structure. Hence, the number of atoms is directly proportional to the number of molecular orbitals formed.

Antibiotics can either kill the target microbes (cidal effect) or can prevent it from pathogenic action (static effect). The former are known as bactericidal and the latter is known as bacteriostatic.

Antibiotics are classified based on the range of microbes that are affected by it. Broad spectrum antibiotics affect Gram-positive as well as Gram-negative bacteria. Narrow spectrum are used only against either Gram-positive or Gram-negative bacteria, whereas limited spectrum antibiotics kill or inhibit only one particular organism.

Antimalarials and antibiotics are ingested in the form of pills. Antiseptics are applied on the skin. Disinfectants are used for cleaning objects like floors, toilets, drains, etc. and protect them from pathogenic activity.

Bithionol consists of two dichloro and dihydroxy substituted aromatic rings connected by a sulphur bridge. It is added to soaps as an antiseptic. It also helps to reduce the smell produced by microbial decomposition on the skin.

Progesterone is a hormone that is known to suppress ovulation. Antifertility drugs are made of synthetic Estrogen and progesterone derivatives. Ethynylestradiol is a drug with a combination of these two derivatives.

The three reactions are as follows:

• Reaction 1: Aniline on treatment with bromine water gives 2,4,6-tribromoaniline.
• Reaction 2: This on diazotisation with HNO₂ gives 2,4,6-tribromobenzenediazonium chloride.
• Reaction 3: This on reaction with H₃PO₂, reduces the diazo group to hydrogen, to give 1,3,5-tribromobenzene.

Coupling reactions of diazonium salts produce azo compounds which are coloured in nature. This is used as an application in the manufacturing of dyes.

m-Bromotoluene cannot be prepared from the direct bromination of toluene or by Friedel-Crafts alkylation of bromobenzene, because of the ortho, para directing nature of alkyl groups.