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

Which of the following is a natural polymer ? Buna-S, Proteins, PVC

Why does NH₃ act as a Lewis base?

What is the two dimensional coordination number of a molecule in square close packed layer?

A compound forms hexagonal close-packed structure. What is the total number of voids in 0.5 mol of it? How many of these are tetrahedral voids?

A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3^rdof tetrahedral voids. What is the formula of the compound?

How many lattice points are there in one unit cell of the following lattice?

Face-centred cubic

A cubic solid is made of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body-centre. What is the formula of the compound? What are the coordination numbers of P and Q?

Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.

Aluminium crystallises in a cubic close-packed structure. Its metallic radius is 125 pm.

1. What is the length of the side of the unit cell?
2. How many unit cells are there in 1.00 cm³ of aluminium?

The cell in which the following reactions occurs:

\[\ce{2Fe^{3+}_{( aq)} + 2I^-_{ (aq)} -> 2Fe^{2+}_{( aq)} + I2_{(s)}}\] has \[\ce{E^\circ_{cell}}\] = 0.236 V at 298 K. 

Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.

What will be the effect of temperature on rate constant?

The rate of the chemical reaction doubles for an increase of 10 K in absolute temperature from 298 K. Calculate E_a.

The activation energy for the reaction \[\ce{2 HI_{(g)} -> H2_{(g)} + I2_{(g)}}\] is 209.5 kJ mol⁻¹ at 581 K. Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?

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.