Science (English Medium) Class 12 - CBSE Question Bank Solutions for Chemistry

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?

Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.

Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?

Describe the preparation of potassium dichromate from iron chromite ore. What is the effect of increasing pH on a solution of potassium dichromate?

Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with iron (II) ions? Write the ionic equation for the reaction.

Give an example and suggest a reason for the following feature of the transition metal chemistry:

The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

Give an example and suggest a reason for the following feature of the transition metal chemistry:

A transition metal exhibits the highest oxidation state in oxides and fluorides.

Give an example and suggest a reason for the following feature of the transition metal chemistry:

 The highest oxidation state is exhibited in oxoanions of a metal.

Indicate the steps in the preparation of K₂Cr₂O₇ from chromite ore.

Indicate the steps in the preparation of KMnO₄ from pyrolusite ore.

Write the formula for the given coordination compound:

Tetraamminediaquacobalt (III) chloride

Write the formula for the given coordination compound:

Potassium tetracyanidonickelate (II)