# CBSE Solved Paper for Class 11 Chemistry Exam 2018

Mayank Uttam

Solved Chemistry paper for Class 11 final exam is available here. This paper is based on latest CBSE Class 11 Chemistry Syllabus. Examination pattern of this solved papers similar to the latest CBSE Sample Paper.

In most of the CBSE Schools, final Class 11 exams will start from March 2018. Now, students should focus more on practice and revision, rather than studying new topics. This solved Chemistry practice paper is important for practice as well as revision. This paper contains important question from fi Class 11 Chemistry NCERT textbook.

Format of CBSE Class 11 Chemistry Paper:

• All questions are compulsory
• There are 26 questions in total. Questions 1 to 5 carry one mark each; questions 6 to 10 carry two marks each, questions 11 to 22 carry three marks each, question 23 carry four marks and questions 24 to 26 carry 5 marks each
• There is no overall choice
• Use of calculator is not permitted
• You may use the following physical constants wherever necessary

CBSE Class 11 Chemistry Syllabus 2017 – 2018

Some sample questions from the paper are given below:

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Question: What is the value of the gas constant (in SI Units)?

Solution:

8.314 J K‒1 mol‒1.

Question: Arrange the following molecular species in increasing order of stability.

N2, N2+, N2, N22‒

Solution:

Correct order is: N2 > N2+ = N2> N22‒

Question: Find the equivalent temperature 10o in Fahrenheit.

Solution:

oF = 9/2 (oC) + 32 = 9/2 (10) + 32 = 50o.

Class 11th Chemistry NCERT Solutions

Question: Define the term solution?

Solution:

It is defined as a homogenous mixture of two or more chemically non-reacting substances, the relative amounts of which can be varied upto a certain limit.

Question: What do you understand by extensive properties?

Solution:

Extensive properties are those which depend upon the amount of substance taken.

Question: Find the atomicity of propane molecule?

Solution:

Propane is C2H8. Its atomicity = 3 + 8 = 11.

Question: What is modern periodic law?

Solution:

According to this law states that physical and chemical properties of the elements are a periodic functions of their atomic numbers.

Question: Define bonding molecular orbital.

Solution:

Molecular orbitals formed by combination of atomic orbitals of comparable energy and proper orientation which have smaller energies than those of combining orbitals.

Question: What is the relation between molecular mass and vapour density of gas?

Solution:

Molecular mass = 2 × Vapour Density.

Question: What is triple point?

Solution:

The temperature at which all three states of matter or phases of the same substance exist together. E.g. water, ice and water vapour exist together at 0.01o C (273.16 K) and 4.58 mm pressure.

Question:

What is 3rd law of thermodynamics?

Solution:

The entropy of a perfectly crystalline solid approaches zero as the temperature approaches absolute zero.

We can also say that the entropy of all perfectly crystalline solids may be taken as zero at the absolute zero of temperature.

As, entropy is a measure of disorder, the above definition may be given molecular interpretation as follows

At absolute zero, a perfectly crystalline solid has a perfect order of its constituent particles, i.e., there is no disorder at all. Hence, the absolute entropy is taken as zero.

Question: Why molality is preferred over molarity in expressing the concentration of a solution?

Solution:

According to the definition, molality is the number of moles of the solute present in 1 kg of the solvent whereas molarity is the number of moles of the solute present per litre of the solution. So, molality involves only masses which do not change with temperature whereas molarity involves volume which changes with temperature. Therefore, molality is preferred over molarity.

Question: Write some differences between the terms electron gain enthalpy & electronegativity?

Solution:

Electron gain enthalpy refers to the tendency of an isolated gaseous atom to accept an additional electron to form a gaseous negative ion, electronegativity refers to the tendency of the atom of an element to attract the shared pair of electrons towards it in a covalent bond.

NCERT Exemplar: CBSE Class 11 Chemistry – All Chapters

Question:

Write some important information you can obtain from the magnitude of equilibrium constant.

Solution:

(a) Low value of K (<10‒3) shows that backward reaction is favoured, i.e., concentration of reactants is much larger than that of the products.

(b) Intermediate value of K (10‒3 to 103) shows that the concentration of the reactants and products are comparable.

(c) Large value of equilibrium constant (>103) shows that forward reaction is favoured, i.e., concentration of products is much larger than that of the reactants at equilibrium.

Question:

Explain why law of conservation of mass should more appropriate to be called as law of conservation of mass and energy.

Solution:

In nuclear reactions, it is observed that the mass of the products is less than the mass of the reactants. The difference of mass, called the mass defect, is converted into energy according to Einstein equation, E = Δmc2. Therefore, it will be more appropriate to call law of conservation of mass as a law of conservation of mass & energy.

Question:

Prove that the circumference of the Bohr orbit for hydrogen atom is an integral multiple of the de Broglie wavelength associated with the electron moving around the orbit.

Solution:

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