Chemistry Test - 9

Transition elements are characterized by partially filled (n-1) d subshells.

Zn, Cd and Hg are not regarded as transition elements as they have completely filled (n-1)d subshell.

The electronic configuration of zinc is [Ar]3d¹⁰4s².

The electronic configuration of cadmium is [Kr]4d¹⁰5s².

The electronic configuration of mercury is [Xe]5d¹⁰6s².

An optically active substance is one which can rotate the plane of polarisation of plane polarised light. if you shine a beam of polarised monochromatic light (light of only a single frequency – in other words a single colour) through a solution of an optically active substance, when the light emerges, its plane of polarisation is found to have rotated.

Aniline-water mixture is separated by employing the process of steam distillation. Steam distillation method is used when the substances involved are steam volatile and immiscible in water. Aniline satisfies both these conditions and, hence, this method is used to separate aniline from aniline-water mixture. Glycerol-spent lye mixture is an example of distillation under reduced pressure, chloroform and aniline mixture employs simple distillation, and crude oil separation involves fractional distillation method.

Blue litmus paper turns into red litmus paper on contact with an acidic solution.

• A litmus paper test is done to find the solution whether it is Acidic or Basic in nature.
• Litmus paper is a type of pH paper made by treating paper with natural dyes from lichens.

Temporary hardness of water can be removed by heating the water. Liming can soften the water with the use of calcium hydroxide, this chemical causes the calcium and magnesium carbonate to precipitate out as well.

A good adsorbent requires large surface area, should be easily available, less expensive. They should also be thermally stable, and have high abrasion resistance. Silica, alumina, and starch possesses these characteristics while potassium permanganate does not, so it cannot be an adsorbent.

• The_complex given here is \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}\) 
• The complex has \(\mathbf{s p}^{3} \mathrm{~d}^{2}\) hybridization which means \(\mathbf{4 d}, \mathbf{4 s}\), and \(4 \mathrm{p}\) orbitals of Cobalt are involved and the cation has \(+3\) charge. 
• The ligand ammonia is a strong field ligand and forms low spin complexes. 
• The cation undergoes hybridisation in the following way-

• Six ligands are attached and it corresponds to C.N number six which gives octahedral geometry.

Haloarenesare much less reactive than haloalkanes towards nucleophilic substitutionreactions due to the following reasons:

1.Resonance effect:  n haloarenes the electron pair on the halogen atom isin conjugation with the π – electrons of the ring and the following resonatingstructures are possible. C-Cl bond acquires a partial double bond character dueto resonance. As a result, the bond cleavage in haloarenes is difficult than incase of haloalkanes and therefore they are less reactive towards nucleophilicsubstitution reactions.

2.The C-Cl bond length in haloalkanes is 177 pm while in haloarenes it is 169 pm.Since it is difficult to break shorter bond than a longer bond. Therefore,haloarenes are less reactive than haloalkanes towards nucleophilic substitutionreactions.

When the ozonolysis of 2-Methyl pent-2-ene take place the products are acetone and propanal.

The pH of water is 7.

The pH scale ranges from 0 to 14. In general, water with a pH < 7 is considered acidic and a pH > 7 is considered basic. The normal range for pH in surface water systems is 6.5 to 8.5 and for groundwater systems 6 to 8.5.