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

The statement that is not correct for periodic classification of elements is ______.

All transition elements are d-block elements, but all d-block elements are not transition elements. Explain

In which of the following molecule/ion all the bonds are not equal?

Which of the following statements are correct about \[\ce{CO^{2-}3}\]?

(i) The hybridisation of central atom is sp³.

(ii) Its resonance structure has one \[\ce{C - O}\] single bond and two \[\ce{C = O}\] double bonds.

(iii) The average formal charge on each oxygen atom is 0.67 units.

(iv) All \[\ce{C - O}\] bond lengths are equal.

All the \[\ce{C - O}\] bonds in carbonate ion \[\ce{(CO^{2-}3)}\] are equal in length. Explain.

Describe hybridisation in the case of \[\ce{PCl5}\] and \[\ce{SF6}\]. The axial bonds are longer as compared to equatorial bonds in \[\ce{PCl5}\] whereas in \[\ce{SF6}\] both axial bonds and equatorial bonds have the same bond length. Explain.

Which of the following arrangements represent increasing oxidation number of the central atom?

Assertion (A): Among halogens fluorine is the best oxidant.

Reason (R): Fluorine is the most electronegative atom.

Assertion (A): In the reaction between potassium permanganate and potassium iodide, permanganate ions act as oxidising agent.

Reason (R): Oxidation state of manganese changes from +2 to +7 during the reaction.

Which of the following equations depict the oxidising nature of \[\ce{H2O2}\]?

Which of the following equation depicts reducing nature of \[\ce{H2O2}\]?

Some of the properties of water are described below. Which of them is/are not correct?

(i) Water is known to be a universal solvent.

(ii) Hydrogen bonding is present to a large extent in liquid water.

(iii) There is no hydrogen bonding in the frozen state of water.

(iv) Frozen water is heavier than liquid water.

If same mass of liquid water and a piece of ice is taken, then why is the density of ice less than that of liquid water?

Give reasons: Lakes freeze from top towards bottom.

Give reasons: Ice floats on water.

\[\ce{H2O2}\] is a better oxidising agent than water. Explain.

Melting point, enthalpy of vapourisation and viscosity data of \[\ce{H2O}\] and \[\ce{D2O}\] is given below :

On the basis of this data explain in which of these liquids intermolecular forces are stronger?

Explain why \[\ce{HCl}\] is a gas and \[\ce{HF}\] is a liquid.

Why does water show high boiling point as compared to hydrogen sulphide? Give reasons for your answer.

How will you account for 104.5° bond angle in water?