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 decomposition of N₂O₅ at various temperatures is given below:

Draw a graph between ln k and `1/T` and calculate the values of A and E_a. Predict the rate constant at 30º and 50ºC.

The rate constant for the decomposition of hydrocarbons is 2.418 × 10⁻⁵ s⁻¹ at 546 K. If the energy of activation is 179.9 kJ/mol, what will be the value of pre-exponential factor?

Consider a certain reaction \[\ce{A -> Products}\] with k = 2.0 × 10⁻² s⁻¹. Calculate the concentration of A remaining after 100 s if the initial concentration of A is 1.0 mol L⁻¹.

The decomposition of hydrocarbon follows the equation

k = `(4.5 xx 10^11 s^-1) e^(-28000 K//T)`

Calculate E_a.

The decomposition of A into product has value of k as 4.5 × 10³ s⁻¹ at 10°C and energy of activation 60 kJ mol⁻¹. At what temperature would k be 1.5 × 10⁴ s⁻¹?

The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate the energy of activation of the reaction assuming that it does not change with temperature.

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 role does adsorption play in heterogeneous catalysis?

Give four examples of heterogeneous catalysis.

Out of C and CO, which is a better reducing agent at 673 K?

Giving examples, differentiate between ‘roasting’ and ‘calcination’.

Why copper matte is put in silica lined converter?

Out of C and CO, which is a better reducing agent for ZnO?

Give evidence that [Co(NH₃)₅Cl]SO₄ and [Co(NH₃)₅SO₄]Cl are ionisation isomers.

Write the free radical mechanism for the polymerisation of ethene.