CBSE Class 12th Physics, Chemistry and Biology Solved Guess Papers 2018

Due to this reason, we have provided a complete package for the Class 12th students having Physics, Chemistry and Biology subjects. These papers are 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 are frequently asked in board exams, every year. These papers contain all such important concepts. These papers are based on latest examination pattern.

Highlights of the complete package:

• There are total 3 eBooks
• Each subject (Physics, Chemistry and Biology) carries 1 eBook
• Ideal to understand exam pattern and marking trends
• Strictly follows the CBSE marking scheme
• Focuses on the questions which needs the proper explanation
• Offers detailed explanation and solution for each and every question
• Helps in building student's confidence for the final exam
• Perfect for practice

CBSE Class 12 Syllabus 2017-2018: All Subjects

More details about the 3 Guess Papers of this package:

Class 12th Chemistry Guess Paper:

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)

Some sample questions from the Chemistry Guess Paper are given below:

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^‒)

CBSE Class 12 Sample Paper 2018: All Subjects

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 d²sp³hybridization.

(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.

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Other questions and solutions are present in the PDF (Link is given at the end of this article)

Class 12th Physics Guess Paper:

In this solved Guess Paper, there are 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 Physics Examination Pattern 2017 – 2018)

Some sample questions of this solved guess paper are given below:

Question: Define current sensitivity of a galvanometer?

Answer:

Current sensitivity of a galvanometer is defined as deflection produced in the galvanometer when a unit current flows through it.

Question: Why is soft iron core preferred for making the core of a transformer?

Answer:

As, the area of hysteresis loop for soft iron is very small so, energy dissipated per unit volume per cycle of magnetisation is small.

Question: Write two ways by which the range of transmission can be increased?

Answer:

Range of transmission of T.V. signal can be increase

• By increasing the power of transmitting signal from TV station

• By increasing the heights of transmitting and receiving antenna

Question: What is meant by ‘half-life’ of a radioactive element? What percentage of a given mass of a radioactive substance will be left undecayed after four half lives?

Answer:

The time interval in which the number of atoms of a radioactive element decays to one-half of its initial value is called half-life of the element.           

If N_o is the initial quantity of radioactive element, then the quantity N of the element left after n half-live is given by: N = N_o(1/2)ⁿ.

The amount of substance left after 4 half lives can be given as:

N = N_o(1/2)⁴ = N_o/16 or 6.25% of initial value.

Question:

Arrange the following electromagnetic radiations in ascending order of their frequencies:

(i) Microwaves

(ii) Radio waves

(iii) X-rays

(iv) Gamma rays

Write two uses of any two of these.

Answer:

Given electromagnetic radiations in ascending order of their frequencies are: Radio waves, microwaves, ultraviolet rays, X-rays and gamma
rays.
Uses of Electromagnetic Spectrum

(i) Gamma-rays are highly penetrating. They can penetrate thick iron blocks. Due to high energy, they are used to produce nuclear reactions. g-rays are produced in nuclear reactions. In medicine, they are used to destroy cancer cells.

(ii) X-rays are used in medical diagnostics to detect fractures in bones, tuberculosis of lungs,
presence of stone in gallbladder and kidney. They are used in engineering to check flaws in
bridges. In physics X-rays are used to study crystal structure.

Question: Amit is a resident of Tamil Nadu was all set to leave everything and shift to another place in view of the decision of Government to start nuclear thermal power plant at Tamil Nadu. His granddaughter Rashi, a science student was really upset on the ignorant decision of her grandfather. She could finally convince him not to shift, since adequate safety measures to avoid any nuclear mishap have already been taken by the Government before starting nuclear thermal power plants.

(i) What is the value displayed by Rashi in convincing her grandfather?

(ii) What is the principle behind working of nuclear reactor?

(iii) What are the main components of nuclear reactor?

(iv) Why is heavy water used as moderator?

Answer:

(i) Rashi is attached to her native place.

(ii) A Nuclear reactor works on the principle of nuclear fission

(iii) Moderator, Cadmium rods

(iv) Heavy water (D₂O) is used to slow down the speed of fast moving neutrons.

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Other questions and solutions are present in the package (Link is given at the end of this article)

Class 12th Biology Guess Paper:

In this solved Guess Paper, you will find 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 as per latest CBSE Class 12 Biology Examination Pattern 2017 – 2018.

Some sample questions of this solved guess paper are given below:

Question: Mention the role of 'genetic mother' in MOET.

Answer.

Multiple Ovulation Embryo Transfer (MOET) includes administration of hormones to genetic mother to induce production of more number of mature eggs at a time, i.e. superovulation, which in turn are then transferred to surrogate mother.

Question: Name the technique used to separate DNA fragments in a laboratory?

Answer. Gel Electrophoresis is used to separate DNA fragments in a laboratory.

Question: If 60 children were born in a hospital out of which 6 children died in a week, then what would be the death rate of children in that hospital?

Answer. Death rate of children for the mentioned period is 0.1 child per week.

Question: What is the principle involved in natural methods of birth control.

Answer.

Natural or traditional methods are based on the principle of avoiding chances of meeting of sperms and eggs. These include periodic abstinence, Coitus interrupts and lactational amenorrhoea.

Question: A certain tissue, of a plant, infected with TMV was used to obtain a new plant using tissue culture technique. Identify the technique used and reason out the possibility of obtaining a new healthy plant.

Answer. Tissue culture using meristematic tissue as it is virus free.

Question: Name a genus of baculovirus. Why they are considered good biocontrol agents?

Answer.

Nucleopolyhedrovirus. Being species specific selective and narrow spectrum biocontrol agents, these viruses do not exert any harmful impact on crops, animals and human and non target insects. For example, Nucleopolyhedrovirus targets mainly moths and butterflies.

Question: A single pea plant in your kitchen garden produces pods with viable seeds, but individual papaya plant does not. Explain.

Answer.

Pea plant is a dioecious plant and produce bisexual flowers bearing both stamen and pistel on the same flower. Therefore, self fertilization between pollen and ovule of same flowers produce viable seeds. Papaya is a monoecious plant and produce unisexual flowers which in turn facilitate only cross fertilization. Hence, single papaya plant cannot produce viable seeds.

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Other questions and solutions are present in the PDF (Link to access the complete file is given below)

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