Ans. The ionic radius of Be²⁺ is estimated to be 31 pm : the charge/ radius ratio is nearly the same as that of the Al³⁺ ion. Hence beryllium resembles aluminium in some ways. Some of the similarities are:

• Like aluminum, beryllium is not readily attacked by acids because of the presence of an oxide film on the surface of the metal.
• Beryllium hydroxide dissolves in excess of alkali to give a beryllate ion, just as aluminium hydroxide gives aluminate ion.
• The chlorides of both beryllium and aluminium have Cl- bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong Lewis acids. They are used as Friedel Craft catalysts.
• Beryllium and aluminium ions have strong tendency to form complexes.

The limiting reagent (or limiting reactant) in a chemical reaction is the substance that is totally consumed when the chemical reaction is complete. The amount of product formed is limited by this reagent, since the reaction cannot continue without it.

Ans. No. of moles of CO₂ present=given mass /molar mass

=> 4.4/44 = 0.1 moles

No. of moles = given vol. / 22.4 litres

=> 0.1= given vol./22.4 litres

=> 0.1*22.4 = given vol.

Given vol is the required vol. here,

So the vol. occupied by 4.4g of CO₂ is 2.24 litres.

Due  to extra stability of half filled orbital.

Ans. Principle of paper chromatography: The principle involved is partition chromatography wherein the substances are distributed or partitioned between liquid phases. One phase is the water, which is held in the pores of the filter paper used; and other is the mobile phase which moves over the paper. The compounds in the mixture get separated due to differences in their affinity towards water (in stationary phase) and mobile phase solvents during the movement of mobile phase under the capillary action of pores in the paper.

The principle can also be adsorption chromatography between solid and liquid phases, wherein the stationary phase is the solid surface of paper and the liquid phase is of mobile phase.

But most of the applications of paper chromatography work on the principle of partition chromatography, i.e. partitioned between to liquid phases.

Ans. Entropy is a thermodynamic state quantity which is a measure of randomness or disorder of the molecules of the system.

Ans. In large ions, the charge is distributed over a large area, because of which the charge per unit volume is less. Therefore the hold of the nucleus on the outermost electrons is less, because of which the electronic distribution in these ions can be easily disturbed (or they can be easily polarised), when a small ion comes closer to these ions.

Ans. 

This is due to the fact that dipole moment is a vector quantity and hence resultant dipole moment in a molecule will depend upon the direction of dipole moments of individual bonds.

Nitrogen has a lone pair of electrons and is more electronegative than hydrogen. So, in case of NH₃, the orbital moment due to the lone pair of electrons on nitrogen is in the same direction of the 3 N-H dipoles.Thus, the molecule has a net dipole moment and it is polar.

In NF₃, fluorine being more electronegative than nitrogen pulls the shared pair of electrons of the N-F bonds towards itself. Because of this, the orbital moment due to lone pair of electrons and the resultant dipole moment of 3 N-F bonds point in the opposite directions to that of lone pair of electrons. This lowers the dipole moment of NF₃.

Ans. A Nucleophile is a chemical species that donates an electron pair to an electrophile to form a chemical bond in relation to a reaction. All molecules or ions with a free pair of electrons or at least one pi bond can act as Nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.

Caesium (Cs)  Since it has low ionisation enthalpy.

Fluorine is more electronegative than chlorine. Hence, HF has more polarity than HCl. 

Answer:

<a href="http://socratic.org/chemistry/solutions-and-their-behavior/molarity">Molarity</a> is the concentration of a solution expressed as the number of moles of solute per litre of solution.

Explanation:

To get the molarity, you divide the moles of solute by the litres of solution

Molarity=moles of solute / litres of solution

Molarity decreases when temperature increases.

Explanation:

Molarity is affected by temperature because it is based on the volume of the solution, and the volume of a substance will be affected by changes in temperature.

In general, volume will increase when temperature increases, and vice versa. So if we use an example where temperature is increasing, that means the L in that equation is getting larger as well. Since we are dividing by L, (and dividing by a larger number gives a smaller answer,) M will become smaller.

Ans. (i)Distillation Under Reduced Pressure is used for purifying or separating thermally unstable liquid compounds.

Uses :

• In Petroleum Refining
• in food processing

(ii) For testing of sulphur present in the organic compound, the Lassaigne’s extract is acidified with acetic acid (CH₃COOH) and not sulphuric acid because lead acetate is soluble and does not interfere with the test. If sulphuric acid (H₂SO₄ ) is used, lead acetate will react with H₂SO4 itself to form white ppt. PbSO_4.

The cyclopropenyl cation is the smallest aromatic substance.

As to π electrons, when n = 0, the ordinary cyclopropene molecule is not aromatic. It becomes aromatic only if the third π electron is missing. That is, when it becomes the cyclopropenyl cation and its ring has a positive charge.

Ans. 5-oxohexanoic acid

Ans. A buffer solution is one which resists changes in pH when small quantities of an acid or an alkali are added to it.

A common example would be a mixture of ethanoic acid and sodium ethanoate in solution.

The process converts atmospheric nitrogen (N₂) to ammonia (NH₃) by a reaction with hydrogen (H₂) using a metal catalyst under high temperatures and pressures:

hydro what?? 

The usual structural representation for benzene is a six carbon ring (represented by a hexagon) which includes three double bonds. Each of the carbons represented by a corner is also bonded to one other atom. In benzene itself, these atoms are hydrogens. The double bonds are separated by single bonds so we recognize the arrangement as involving conjugated double bonds. An alternative symbol uses a circle inside the hexagon to represent the six pi electrons. Each of these symbols has good and bad features. We'll use the three double bond symbol simply because it is also routinely used in the text.

Keep in mind that if the hexagon contains neither the three double bonds nor the circle, the compound is not aromatic. It is simply cyclohexane and there are two hydrogens on each carbon atom. This is easy to mistake when hurrying, so be careful when you are intepreting any structural formulas which include hexagons.

In short,  the inert pair effect is a tendency of the electrons in the outermost atomic s orbital to remain unionized or unshared in compounds of post -transition metals .

Ans. Group 13 elements have ns2np1 electronic configuration. Hence they would be expected to be trivalent. In most of their compounds this is the case, however for the heavy elements lower oxidation states are more stable. Group 13 elements have ns²np¹ electronic configuration. Hence they would be expected to be trivalent. In most of their compounds this is the case, however for the heavy elements lower oxidation states are more stable. This is explained by the s electrons remaining paired and not participating in bond formation. This inertness of s-subshell electrons towards the bond formation is called inert pair effect. This happens because the s orbitals are held closer to the nucleus, therefore the electrons present in s orbitals are held strongly by nucleus because of large electrostatic forces. Hence the energy required to unpair the s-electrons is high because of which they remain paired.

This is explained by the s electrons remaining paired and not participating in bond formation. This inertness of s-subshell electrons towards the bond formation is called inert pair effect.

This happens because the s orbitals are held closer to the nucleus, therefore the electrons present in s orbitals are held strongly by nucleus because of large electrostatic forces.

Hence the energy required to unpair the s-electrons is high because of which they remain paired.