Science (English Medium) कक्षा ११ - CBSE Question Bank Solutions for Chemistry

Why does the boundary between liquid phase and gaseous phase disappear on heating a liquid upto critical temperature in a closed vessel? In this situation what will be the state of the substance?

In which of the following reactions, the equilibrium remains unaffected on addition of small amount of argon at constant volume?

Assertion (A): In the dissociation of \[\ce{PCl5}\] at constant pressure and temperature addition of helium at equilibrium increases the dissociation of \[\ce{PCl5}\].

Reason (R): Helium removes \[\ce{Cl2}\] from the field of action.

Calculate the strength of 5 volume \[\ce{H2O2}\] solution.

An acidic solution of hydrogen peroxide behaves as an oxidising as well as reducing agent. Illustrate it with the help of a chemical equation.

With the help of suitable examples, explain the property of \[\ce{H2O2}\] that is responsible for its bleaching action?

Why can dilute solutions of hydrogen peroxide not be concentrated by heating. How can a concentrated solution of hydrogen peroxide be obtained?

Phosphoric acid is preferred over sulphuric acid in preparing hydrogen peroxide from peroxides. Why?

Illustrate oxidising, reducing and acidic properties of hydrogen peroxide with equations.

A colourless liquid ‘A’ contains H and O elements only. It decomposes slowly on exposure to light. It is stabilised by mixing urea to store in the presence of light. Write chemical equations for its decomposition reaction in light.

Hyperconjugation involves delocalisation of:

(i) Electrons of carbon-hydrogen σ bond of an alkyl group directly attached to an atom of unsaturated system.

(ii) Electrons of carbon-hydrogen σ bond of alkyl group directly attached to the positively charged carbon atom.

(iii) π-electrons of carbon-carbon bond.

(iv) Lone pair of electrons.

If the position of the electron is measured within an accuracy of ± 0.002 nm, calculate the uncertainty in the momentum of the electron. Suppose the momentum of the electron is h/4π_m × 0.05 nm, is there any problem in defining this value.

Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction:

\[\ce{CH4 (g) + H2O (g) ⇌ CO (g) + 3H2 (g)}\]

Write as the expression for K_p for the above reaction.

Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction:

\[\ce{CH4 (g) + H2O (g) ⇌ CO (g) + 3H2 (g)}\]

How will the values of Kp and composition of equilibrium mixture be affected by

1. increasing the pressure
2. increasing the temperature
3. using a catalyst?

At 473 K, equilibrium constant K_c for decomposition of phosphorus pentachloride, PCl₅is 8.3 ×10^-3. If decomposition is depicted as,

\[\ce{PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)}\]  Δ_rH° = 124.0 kJmol^–1

Write an expression for K_c for the reaction.

At 473 K, equilibrium constant K_c for decomposition of phosphorus pentachloride, PCl₅is 8.3 ×10^-3. If decomposition is depicted as,

\[\ce{PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)}\]  Δ_rH° = 124.0 kJmol^–1

What is the value of K_c for the reverse reaction at the same temperature?

At 473 K, equilibrium constant K_c for decomposition of phosphorus pentachloride, PCl₅ is 8.3 ×10^-3. If decomposition is depicted as,

\[\ce{PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)}\]  Δ_rH° = 124.0 kJmol^–1

What would be the effect on K_c if

1. more PCl₅ is added
2. pressure is increased?
3. The temperature is increased?

Which of the following is responsible to rule out the existence of definite paths or trajectories of electrons?

Table-tennis ball has a mass 10 g and a speed of 90 m/s. If speed can be measured within an accuracy of 4% what will be the uncertainty in speed and position?

The effect of uncertainty principle is significant only for motion of microscopic particles and is negligible for the macroscopic particles. Justify the statement with the help of a suitable example.