Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

Write the names of monomers used for getting the following polymer:

Neoprene

Give the structures of A, B and C in the following reactions :

Give the structures of A, B and C in the following reactions :

Define the following terms : Molarity

Complete the following equations:Cr₂O₇^2- + 2OH^- →

Complete the following equations : MnO₄- + 4H⁺ + 3e^- →

Complete the following equation : MnO₄^- + 8H⁺ + 5e^- →

Write the principle behind the froth floatation process. What is the role of collectors in this process?

Complete the following chemical equation

Cr₂O₇^2- + 3Sn²⁺ + 14H⁺ →

Gold (atomic radius = 0.144 nm) crystallises in a face-centred unit cell. What is the length of a side of the cell?

Write the Nernst equation and emf of the following cell at 298 K:

Mg_(s) | Mg²⁺ (0.001 M) || Cu²⁺ (0.0001 M) | Cu_(s)

Calculate the half-life of a first order reaction from the rate constant given below:

200 s⁻¹

The half-life for radioactive decay of ¹⁴C is 5730 years. An archaeological artifact containing wood had only 80% of the ¹⁴C found in a living tree. Estimate the age of the sample.

The experimental data for decomposition of N₂O₅.

\[\ce{2N2O5 -> 4NO2 + O2}\] in gas phase at 318 K are given below:

1. Plot [N₂O₅] against t.
2. Find the half-life period for the reaction.
3. Draw a graph between log [N₂O₅] and t.
4. What is the rate law?
5. Calculate the rate constant.
6. Calculate the half-life period from k and compare it with (ii).

During nuclear explosion, one of the products is ⁹⁰Sr with half-life of 28.1 years. If 1μg of ⁹⁰Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically.

The rate constant for the first order decomposition of H₂O₂ is given by the following equation:

log k = 14.34 − 1.25 × 10⁴ K/T. 

Calculate E_a for this reaction and at what temperature will its half-period be 256 minutes?

What is an adsorption isotherm?

Describe Freundlich adsorption isotherm.

How is activation of adsorbent achieved?

What is the role of depressant in froth floatation process?