Science (English Medium) Class 11 - CBSE Question Bank Solutions

Use the information and data given below:

• Strength of London forces increases with the number of electrons in the molecule.

Looking at the trend of boiling points of \[\ce{HCl, HBr and HI}\], explain out of dipole-dipole interaction and London interaction, which one is predominant here.

At a particular temperature and atmospheric pressure, the solid and liquid phases of a pure substance can exist in equilibrium. Which of the following term defines this temperature?

(i) Normal melting point

(ii) Equilibrium temperature

(iii) Boiling point

(iv) Freezing point

Match the following equilibria with the corresponding condition:

Explain redox reactions on the basis of electron transfer. Give suitable examples.

Hydrogen resembles halogens in many respects for which several factors are responsible. Of the following factors which one is most important in this respect?

Radioactive elements emit α, β and γ rays and are characterised by their half-lives. The radioactive isotope of hydrogen is ______.

Dihydrogen reacts with dioxygen \[\ce{(O2)}\] to form water. Write the name and formula of the product when the isotope of hydrogen which has one proton and one neutron in its nucleus is treated with oxygen. Will the reactivity of both the isotopes be the same towards oxygen? Justify your answer.

Metal carbonates decompose on heating to give metal oxide and carbon dioxide. Which of the metal carbonates is most stable thermally?

The s-block elements are characterised by their larger atomic sizes, lower ionisation enthalpies, invariable +1 oxidation state and solubilities of their oxosalts. In the light of these features describe the nature of their oxides, halides and oxosalts.

The geometry of a complex species can be understood from the knowledge of type of hybridisation of orbitals of central atom. The hybridisation of orbitals of central atom in [Be(OH)₄]^– and the geometry of the complex are respectively.

Which of the following oxides is acidic in nature?

The exhibition of highest co-ordination number depends on the availability of vacant orbitals in the central atom. Which of the following elements is not likely to act as central atom in \[\ce{MF^{3-}6}\]?

Ionisation enthalpy (∆_iH₁kJ mol^–1) for the elements of Group 13 follows the order.

In the structure of diborane ______.

A compound X, of boron reacts with NH₃ on heating to give another compound Y which is called inorganic benzene. The compound X can be prepared by treating BF₃ with Lithium aluminium hydride. The compounds X and Y are represented by the formulas.

The most commonly used reducing agent is ______.

Dry ice is ______.

Cement, the important building material is a mixture of oxides of several elements. Besides calcium, iron and sulphur, oxides of elements of which of the group (s) are present in the mixture?

Which of the following statements are correct. Answer on the basis of Figure.

(i) The two birdged hydrogen atoms and the two boron atoms lie in one plane;

(ii) Out of six B – H bonds two bonds can be described in terms of 3 centre 2-electron bonds.

(iii) Out of six B – H bonds four B – H bonds can be described in terms of 3 centre 2 electron bonds;

(iv) The four-terminal B – H bonds are two centre-two electron regular bonds.

Explain why the following compounds behave as Lewis acids?

BCl₃