CBSE Class 12th Chemistry Solved Guess Paper: 2018

Solved Guess Paper for Class 12 Chemistry CBSE Board exam 2018 is available here. With this Guess Paper, students can easily understand the latest CBSE Class 12 Chemistry examination pattern & marking scheme.

CBSE Class 12 Chemistry Board exam 2018 is scheduled to be held on 13 March. It means very few days are left for board exam preparation. CBSE Class 12 Chemistry Syllabus is vast; there are 16 Chapters in Class 12 Chemistry NCERT textbooks. Hence, the selective study in this subject plays a very important role. Due to this reason, we have provided a completely solved CBSE Class 12 Chemistry Solved Guess Paper for 2018 board exams.

This solved guess paper is specially prepared for Class 12 Chemistry board exam 2018. This paper is developed by subject experts at Jagranjosh.com after the brief analysis of previous 5 years’ papers. After going through previous year papers, our subject experts have observed that questions based on some important concepts of Class 12 Chemistry Syllabus are frequently asked in board exams, every year. The paper contains all such important concepts.

CBSE Class 12 Chemistry Sample Paper: 2018

This solved Guess Paper has 5 sections (i.e., Section A, Section B, Section C, Section D and Section E)

• Section ‒ A contains question number 1 to 5 (very Short Answer type questions of one mark each)

• Section ‒ B contains question number 6 to 10 (Short Answer type I questions of two marks each)

• Section ‒ C contains question number 11 to 22 (Short Answer type II questions of three marks each)

• Section ‒ D contains question number 23 (value Based Question of four marks)

• Section ‒ E contains question number 24 to 26 (Long Answer type questions of five marks each)

Internal choices are present in short answer types questions and long answer type questions (According to latest CBSE Class 12 Chemistry Examination Pattern 2017 – 2018)

Salient features of this Solved Guess Paper are:

• Strictly follows latest CBSE Class 12th Chemistry syllabus

• Based on latest examination pattern

• Blueprint of this guess paper is almost similar to the latest CBSE Cass 12 Chemistry Sample Paper

• Focuses upon topics from which questions are likely to be asked

• Offers detailed solutions for each and every question

• Perfect for practice & revision

CBSE Class 12th Chemistry Notes: All Chapters

Some questions from the solved guess paper are given below:

Question: Out of CH₃Br or CH₃I, which compound will react faster in S_N2 reaction with —OH? Why?

Solution:

CH₃–I reacts faster than CH₃–Br as iodine is a better leaving group because of its larger size.

Question: Explain the causes of Brownian movement in a colloidal solution?

Solution:

Brownian movement is due to the unequal bombardment of colloidal particles by the molecules of dispersion medium.

Question: NO₂ group shows its effect only at ortho- and para- positions and not at meta- position. Explain

Solution:

The presence of nitro group at ortho- and para-positions withdraws the electron density from the benzene ring and thus facilitates the attack of the nucleophile on haloarene. The carbanion thus formed is stabilised through resonance. The negative charge appeared at ortho- and para- positions with respect to the halogen substituent is stabilised by –NO₂ group while in case of meta-nitrobenzene, none of the resonating structures bear the negative charge on carbon atom bearing the –NO₂ group. So, the presence of nitro group at meta- position does not stabilise the negative charge and no effect on reactivity is observed by the presence of –NO₂ group at meta position.

Question: Name the reagents which are used in the following conversions:

 (i) Butan-2-one to butan-2-ol

(ii) Phenol to 2, 4, 6-tribromophenol

(iii) A primary alcohol to an aldehyde

Solution:

 (i) NaBH₄

(ii) Br₂/H₂O

(iii) Pyridinium chlorochromate (C₂H₅NH⁺CrO₃Cl^‒)

Question: Define the following terms:

(a) Emulsion

(b) Tyndall Effect

(c) Lyophobic colloids

Solution:

(a) Emulsion: It is a colloidal dispersion in which both the dispersed phase and the dispersion medium are liquids.

(b) Tyndall Effect: It is defined as the scattering of light by the colloidal particles present in colloidal solution.

(c) Autocatalysis: It is reaction in which one of the product acts as a catalyst then, it is called autocatalysis.

Question: Give reasons for the following

(i) Nickel does not form low spin octahedral complexes.

(ii) The p-complexes are known for the transition metals only.

(iii) Co²⁺ is easily oxidised to Co³⁺ in the presence of a strong ligand.
Solution:

(i) Nickel does not form low spin octahedral complexes because ‘Ni’ has electronic configuration 3d⁸ 4s², in which two inner d-orbitals are not available which are required to form d²sp³ hybridization.

(ii)  The p-complexes are known for the transition metals only because they have ‘sandwich’ structure in which the metal ion lies between two planar C₅H₅ rings. The bonding involves overlap of p-electrons of the C₅H₅ rings with unfilled d-orbital of the metal. So, that all M–C bonds are identical for their stability.

(iii) Co²⁺ is easily oxidised to Co³⁺ in the presence of a strong ligand because in presence of strong ligand, the 3d electrons pair up leaving two orbitals empty to be involved in d²sp³ hybridisation.

Question: (a) What is the significance of number 6 and 6, 6 in the polymer names nylon-6 and nylon-6, 6?

(b) What is the difference between Buna-N and Buna-S?

(c) Arrange the following polymers in increasing order of their intermolecular forces

Neoprene, Nylon 6, Polyvinyl chloride

Solution:

(a) Nylon-6 is a condensation polymer of only one type of monomer molecules containing 6 carbon atoms. Nylon-6, 6 is a condensation polymer of two types of monomer molecules each containing six carbon atoms.

(b) Buna-N and Buna-S both are copolymers.

Buna-N is copolymer of 1, 3- butadiene & acrylonitrile whereas, Buna-S is copolymer of 1, 3- butadiene & styrene.

(c) In general, Elastomer < Plastic < Fibre, ∴ Neoprene < Polyvinyl chloride < Nylon 6.

Question: Define the following in relation to proteins :

(i) Primary structure

(ii) Denaturation

(iii) Peptide linkage
Solution:

(i) Primary structure of proteins: The sequence in which various amino acids are arranged in a

protein is called its primary structure. Any change in the sequence of amino acids creates

different protein which alters biological functions.

(ii) Denaturation: When a protein in its native form is subjected to physical change like change in temperature or chemical change like change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get uncoiled and proteins lose its biological activity. During denaturation 2° and 3° structures of proteins are destroyed but 1° structure remains intact, e.g., coagulation of egg white on boiling.

(iii) Peptide linkage: A peptide linkage is an amide linkage formed between

‒COOH group of one α-amino acid and NH₂ group of the other amino acid by the elimination of a water molecule.

Question: Observing the growing cases of diabetes and depression among young children, Mr. Amit, the principal of one reputed school organized a seminar in which he invited parents and principals. They all resolved this issue by strictly banning junk food in school s and introducing healthy snacks and drinks like soup, lassi, milk etc in school canteens. They also decided to make compulsory half an hour of daily physical activities for the students in the morning assembly. After six months, Mr. Amit conducted the health survey in most of the schools and discovered a tremendous improvement in the heath of students.

After reading the above passage answer the following question:

(i) What are the values displayed by Mr. Amit?

(ii) As a student, how can you spread awareness about this issue?

(iii) What are the anti-depressant drugs? Give an example.

(iv) Name the sweetening agent used in the preparation of sweets for a diabetic patient.

Solution:

(i) True educationist: The role of education is not to teach the subjects of syllabus only but also give the true knowledge of right and wrong. Being an education in charge Mr. Lugani took the opportunity to spread the awareness of bad effects of junk food and benefits of healthy food on the health of the children.

No difference in words and work: He only not gave the idea but followed that also which reflects his value of no difference in word and work.

(ii) As a student I will organize a small actively camp in my area to attract the children of the society and will tell them the benefits of healthy food and bad effects of junk food through some skit or games. I will poster and collage on that and display it in common public areas like school, club houses etc.

(iii) Anti- depressant drugs are neurologically active drugs. This class of drugs act as mood-changer in case of depression. That is it helps in overcome the depressed mood of suffered person. The action is achieved by affecting the massage transfer mechanism from nerve to receptor.

Example: Iproniazid & phenelzine.

(iv) Aspartame is the most common sweetening agent used in the preparation of sweets for a diabetic patient.

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Other questions and solutions are available in the PDF of the guess paper.

Get the Complete Class 12th Chemistry Solved Guess Paper for CBSE Board Exam 2018