Which one of the following is the strongest base A. Sc(OH)3 B. La(OH)3 C. Lu(OH)3 D. Yb(OH)3

Ans : Sc(OH)₃

Electronic configuration of Cu²⁺ ion in [Cu(NH_3​)_4​]^2+.
Cu²⁺ ion =[Ar]³d⁹4s⁰.
∴Cu²⁺ ion has one unpaired electron.
Magnetic moment of [Cu(NH_3​)₄​]²⁺(μ)=n(n+2)​BM
where, n=no. of unpaired electrons
μ = √1(1+2) ​= √3 ​= 1.73BM
Whereas Ni²⁺ in [Ni(CN)_4​]²⁻,Ti⁴⁺ in TiCl₄​ and Co²⁺ ion [COCl₆​]⁴⁻ has 2,0 and 3 unpaired electrons respectively.

In nuclear physics and nuclear chemistry, the various species of atoms whose nuclei contain particular numbers of protons and neutrons are called nuclides. Nuclides are also characterized by its nuclear energy states (e.g. metastable nuclide ^242mAm). Each nuclide is denoted by chemical symbol of the element (this specifies Z) with the atomic mass number as superscript. Hydrogen (H), for example , consist of one electron and one proton. The number of neutrons in a nucleus is known as the neutron number and is given the symbol N. The total number of nucleons, that is, protons and neutrons in a nucleus, is equal to Z + N = A, where A is called the atomic mass number.

ANSWER: B. Of lanthanoid contraction
This is because of poor screening effect by 4f electrons,which lead to the lanthanoid contraction.Hence,is the reason of Zn and Hf have almost equal atomic size.

B. Hell Vohlard Zelinsky reaction

 Hell Volhard Zelinsky (HVZ) reaction:
This reaction involves alpha bromination of carboxylic acids. Carboxylic acids react with chlorine or bromine in presence of small amount of red phosphorous to give alpha halo carboxylic acids.

Triethyl amine (C₂H₅)₃N is tertiary amine

Purines are compounds that contain a six- membered ring that has nitrogen in it as well. This ring is further fused with an imidazole ring. Thus, purines are structures that have two rings. Purines that are found in the nucleic acids are Adenine (A) and Guanine (G).

Vacancy and Schottky defect which lead to decrease the density both are the types of a stoichiometric defect. In case of Frenkel defect and interstitial defect, there is no change in density of substance.

ANSWER : B. Schottky defect

Vacancy and Schottky defect which lead to decrease the density both are the types of a stoichiometric defect. In case of Frenkel defect and interstitial defect, there is no change in density of substance.

Uses of iodoform (CHI₃)

Iodoform was used earlier as an antiseptic, but now it has been replaced by other formulations-containing iodine-due to its objectionable smell. The antiseptic property of iodoform is only due to the liberation of free iodine when it comes in contact with the skin.

1) Paper Chromatography:

It is the simplest type of chromatography. In this method, a special type of paper called chromatographic paper or ordinary filter paper is used.

A line is drawn near the bottom edge of the paper. The paper is dipped in a solvent and taken in a beaker so that the line drawn on the paper is above the level of the solvent.

Stationary phase: Filter paper

Mobile phase: Solvent

As the solvent rises on the paper, it takes along with it the drop of the substances.

The component of the drop which is more soluble rises faster and we see various spots on the paper, each indicating a component of the mixture.

The paper is then removed from the solvent and dried.

(2) Crystallisation:

This method is based on the differences in the solubility of solids in a liquid.

The process of formation of crystals from a hot saturated solution caused by cooling is called crystallisation. It is a process in which a solution containing more of the solid component is slowly evaporated.

Pure sugar is obtained from its solution in water by the process of crystallisation.

Rhombic sulphur (α-sulphur)

Rhombic sulphur is crystalline in nature and has octahedral shape. On heating the solution of roll sulphur in CS2 we get rhombic sulphur. It is yellow with a melting point of 385.8K and specific gravity 2.06. Rhombic sulphur cannot be dissolved in water but can be dissolved in benzene, ether, alcohol etc.

Monoclinic sulphur (β-sulphur)

When we take a dish and melt rhombic sulphur in that dish we obtain monoclinic sulphur after cooling it. In this process we make two holes in the crust and pour out the remaining liquid. After this we get colourless needle-shaped crystals of β-sulphur when the crust is removed.

The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O. group of the amino acid located three or four residues earlier along the protein sequence.

A physical change is a change in one or more physical properties of matter without any change in chemical properties. In other words, matter doesn't change into a different substance in a physical change. Examples of physical change include changes in the size or shape of matter.

PH₃​(Phosphine) is a hydride of phosphorous. Phosphine is a gas and has pyramidal structure.Phosphorous involved sp3​ hybridized.  Both PH⁴⁺ PH₃​ have sp^3​ hybridisation state for phosphorous.In PH⁴⁺, all the four orbitals are bonded, whereas in PH₃​, there is a lone pair electrons on phosphorous inPH⁴⁺, the H-P-H bond angle is tetrahedral angle of 109.50. But in PH₃​, lone pair-bond pair repulsion is more than bond pair- bond pair repulsion so, that bond angles become less than normal tetrahedral angle.The bond angle in PH_3​ is about 93.60

Thermodynamics, the study of heat, labour, temperature and energy relationships. Thermodynamics is in general terms, concerned with the transition of energy from one position to another and from one form to another. The basic point is that heat is an energy form that corresponds to a specific amount of mechanical activity.

Colloid: A colloid is a heterogeneous mixture whose particles are not as small as solution but they are so small that cannot be seen by naked eye. When a beam of light is passed through a colloid then the path of the light becomes visible. For example milk, smoke etc.
 Properties of a colloid
• A colloid is a heterogeneous mixture.
• The size of particles of a colloid is too small to be individually seen by naked eyes.
• Colloids are big enough to scatter a beam of light passing through it and make its path visible.
• They do not settle down when left undisturbed, that is, a colloid is quite stable.
• They cannot be separated from the mixture by the process of filtration. But, a special technique of separation known as centrifugation can be used to separate the colloidal particles.

The face-centered cubic (fcc) has a coordination number of 12 and contains 4 atoms per unit cell. The body-centered cubic (bcc) has a coordination number of 8 and contains 2 atoms per unit cell. The simple cubic has a coordination number of 6 and contains 1 atom per unit cell.