Class 12

Protein found in a biological system with a unique three-dimensional structure and biological activity is called a native protein. When a protein in its native form, is subjected to a physical change like change in temperature or a chemical change like change in pH, denaturation of protein takes place. Explain the cause.

Hydrogen bonds and other intermolecular interactions connect the amino acid residues in proteins. The hydrogen bonds are disrupted when a physical or chemical change occurs, and the native protein...

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(i) Assertion and reason both are correct statements but reason does not explain the assertion. (ii) Assertion and reason both are correct statements and reason explain the assertion. (iii) Both assertion and reason are the wrong statements. (iv) The assertion is correct statement and reason is the wrong statement. (v) The assertion is the wrong statement and reason is the correct statement. Assertion: Polytetrafluoroethene is used in making non-stick cookware. Reason: Fluorine has the highest electronegativity

Option (i) is correct Teflon is a chemically inert and thermally stable material that is used to make nonstick cookware.

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(i) Assertion and reason both are correct statements but reason does not explain the assertion. (ii) Assertion and reason both are correct statements and reason explain the assertion. (iii) Both assertion and reason are the wrong statements. (iv) The assertion is correct statement and reason is the wrong statement. (v) The assertion is the wrong statement and reason is the correct statement.Assertion: Network polymers are thermosetting. Reason: Network polymers have high molecular mass.

Option (i) is correct During polymerisation, extensive cross linking results in the creation of a three-dimensional network that is rigid, insoluble, and infusible.

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(i) Assertion and reason both are correct statements but reason does not explain the assertion. (ii) Assertion and reason both are correct statements and reason explain the assertion. (iii) Both assertion and reason are the wrong statements. (iv) The assertion is correct statement and reason is the wrong statement. (v) The assertion is the wrong statement and reason is the correct statement. Assertion: For making rubber synthetically, isoprene molecules are polymerised. Reason: Neoprene (a polymer of chloroprene) is a synthetic rubber.

Option (v) is correct Natural rubber is made up of isoprene molecules, while neoprene, a synthetic rubber, is made up of chloroprene polymers.

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(i) Assertion and reason both are correct statements but reason does not explain the assertion. (ii) Assertion and reason both are correct statements and reason explain the assertion. (iii) Both assertion and reason are the wrong statements. (iv) The assertion is correct statement and reason is the wrong statement. (v) The assertion is the wrong statement and reason is the correct statement.Assertion: Polyamides are best used as fibres because of high tensile strength. Reason: Strong intermolecular forces (like hydrogen bonding within polyamides) lead to close packing of chains and increase the crystalline character, hence, provide high tensile strength to polymers.

Option (ii) is correct Polyamides, such as nylon, are the most often used fibres. Because of the strong intermolecular hydrogen connection, they have a high tensile strength.

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(i) Assertion and reason both are correct statements but reason does not explain the assertion. (ii) Assertion and reason both are correct statements and reason explain the assertion. (iii) Both assertion and reason are the wrong statements. (iv) The assertion is correct statement and reason is the wrong statement. (v) The assertion is the wrong statement and reason is the correct statement. Assertion: Olefinic monomers undergo addition polymerisation. Reason: Polymerisation of vinyl chloride is initiated by peroxides/ persulphates.

Option (i) is correct Polymerization of olefins like ethene results in polymers like polythene.

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(i) Assertion and reason both are correct statements but reason does not explain the assertion. (ii) Assertion and reason both are correct statements and reason explain the assertion. (iii) Both assertion and reason are the wrong statements. (iv) The assertion is correct statement and reason is the wrong statement. (v) The assertion is the wrong statement and reason is the correct statement.Assertion: Most of the Synthetic polymers are not biodegradable. Reason: Polymerisation process induces toxic character in organic molecules.

Option (iv) is correct Enzymatic hydrolysis and environmental oxidation do not destroy the majority of synthetic polymers. Toxic characteristics are not produced via polymerization.

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(i) Assertion and reason both are correct statements but reason does not explain the assertion. (ii) Assertion and reason both are correct statements and reason explain the assertion. (iii) Both assertion and reason are the wrong statements. (iv) The assertion is correct statement and reason is the wrong statement. (v) The assertion is the wrong statement and reason is the correct statement. . Assertion: Rayon is a semi-synthetic polymer and is taken as a better choice than cotton fabric. Reason: Mechanical and aesthetic properties of cellulose can be improved by acetylation.

Option (ii) is correct. Rayon is a semi-synthetic polymer that is a better alternative than cotton because acetylation improves the characteristics of cellulose after processing.  

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Which of the following are characteristics of thermosetting polymers? (i) Heavily branched cross-linked polymers. (ii) Linear slightly branched long-chain molecules. (iii) Become infusible on moulding so cannot be reused. (iv) Soften on heating and harden on cooling, can be reused.

Option (i) and (iii) are the answers. Thermosetting polymers have a lot of branching cross links. They can't be used again since they don't melt when heated and can't be remoulded.

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The figure shown a two-slit arrangement with a source which emits unpolarised light. P is a polariser with axis whose direction is not given. If I0 is the intensity of the principal maxima when no polarizer is present, calculate in the present case, the intensity of the principal maxima as well as of the first minima.

Given wave amplitude in perpendicular polarisation $ A_{\perp}=A_{\perp}^{0}(\sin (k x-\omega t)+\sin (k x-\omega t+\phi)) $ wave amplitude in parallel polarisation $ A_{\|}=A_{\|}^{0}(\sin (k...

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AC = CO = D, S1 C = S2 C = d << D A small transparent slab containing material of µ =1.5 is placed along AS2. What will be the distance from O of the principal maxima and of the first minima on either side of the principal maxima obtained in the absence of the glass slab?

According to the question, $ \begin{array}{l} \Delta x=2 d \sin \theta+(\mu-1) L \\ \sin \theta 0=-1 / 16 \end{array} $ From central maxima, $O P=-D / 16$ $ \sin \theta_{1}=\frac{\pm \lambda / 2-d /...

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A helicopter of mass 2000 kg rises with a vertical acceleration of 15 m/s2. The total mass of the crew and passengers is 500 kg. Give the magnitude and direction of the a) force on the floor of the helicopter by the crew and passengers b) action of the rotor of the helicopter on the surrounding air c) force on the helicopter due to the surrounding air

Given, M = 2000 kg helicopter mass m = 500 kg m = 500 kg m = 500 kg m = 500 kg m = 500 kg m = 500 kg Helicopter acceleration with crew and passengers = 15 m/s2 a) Force exerted by the crew and...

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A rectangular box lies on a rough inclined surface. The coefficient of friction between the surface and the box is μ. Let the mass of the box be m. a) at what angle of inclination θ of the plane to the horizontal will the box just start to slide down the plane? b) what is the force acting on the box down the plane, if the angle of inclination of the plane is increased to a > θ c) what is the force needed to be applied upwards along the plane to make the box either remain stationary or just move up with uniform speed? d) what is the force needed to be applied upwards along the plane to make the box move up the plane with acceleration a.

a) As the box starts to slide down the plane, $\mu=\tan \theta$ $ \theta=\tan ^{-1}(\mu) $ b) If $a>\theta$, the angle of inclination will be the angle of repose and the net force acting will be...

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A cricket bowler releases the ball in two different ways a) giving it only horizontal velocity and b) giving it horizontal velocity and a small downward velocity. The speed vs at the time of release is the same. Both are released at a height H from the ground. Which one will have greater speed when the ball hits the ground? Neglect air resistance.

a) $\frac{1}{2} v_{z}^{2}=g H \Rightarrow v_{z}=\sqrt{2 g H}$ Speed at ground is given as: $\sqrt{v_{s}^{2}+v_{z}^{2}}=\sqrt{v_{s}^{2}+2 g H}$ b)$\frac{1}{2} m v_{s}^{2}+m g H$ is the total energy...

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A racing car travels on a track ABCDEFA. ABC is a circular arc of radius 2 R. CD and FA are straight paths of length R and DEF is a circular arc of radius R = 100 m. The coefficient of friction on the road is μ = 0.1. The maximum speed of the car is 50 m/s. Find the minimum time for completing one round.

Time taken from $A$ to $B$ to $C$ $\mathrm{S} 1=$ length $\mathrm{pf}$ path $=3 / 42 \pi(2 \mathrm{R})=300 \pi \mathrm{m}$ $\mathrm{V} 1=$ speed(maximum) along the circular path of the car $...

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When a body slides down from rest along a smooth inclined plane making an angle of 45 degree with the horizontal, it takes time T. When the same body slides down from rest along a rough inclined plane making the same angle and through the same distance, it is seen to take time pT, where p is some number greater than 1. Calculate the coefficient of friction between the body and the rough plane.

The inclined plane angle is $45^{\circ}$ such that $ \begin{array}{l} u=0 \\ s=s \\ t=T \\ a=g \sin 45^{\circ}=g / \sqrt{2} \\ s=u t+1 / 2 a t^{2} \\ s=g T^{2} / 2 \sqrt{2} \end{array} $ $...

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There are three forces F1, F2, and F3 acting on a body, all acting on a point P on the body. The body is found to move with uniform speed. a) show that the forces are coplanar b) show that the torque acting on the body about any point due to these three forces is zero

a) The body's acceleration is zero because the resultant force of the three forces F1, F2, and F3 on a location on the body is zero. The directions of forces F1 and F2 are in the plane of the paper,...

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A bock of mass M is held against a rough vertical wall by pressing it with a finger. If the coefficient of friction between the block and the wall is μ and the acceleration due to gravity is g, calculate the minimum force required to be applied by the ginger to hold the block against the wall?

F is the force exerted by the finger on a body of mass M that is resting on the wall. Using the balanced state as a starting point, $ \begin{array}{l} \mathrm{F}=\mathrm{N} \\ \mathrm{f}=\mathrm{Mg}...

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Block A of weight 100N rests on a frictionless inclined plane of slope angle 30o. A flexible cord attached to A passes over a frictionless pulley and is connected to block B of weight W. Find the weight W for which the system is in equilibrium.

Equilibrium between $A$ or $B$, Then we know that, $\mathrm{mg} \sin 30^{\circ}=\mathrm{F}$ $ \begin{array}{l} 1 / 2 \mathrm{mg}=\mathrm{F} \\ \mathrm{F}=(1 / 2)(100)=50 \end{array} $ Therefore,...

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A mass of 2 kg is suspended with thread AB. Thread CD of the same type is attached to the other end of 2 kg mass. Lower thread is pulled gradually harder and harder in the downward direction so as to apply force on AB. Which of the threads will break and why?

As the mass 2 kg acts downward, the force acting on the thread AB is equal to the force F. As a result, the force exerted on the AB is 2 kg more than on the D, and the thread AB breaks.

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Compound ‘A’ with molecular formula C4H9Br is treated with aq. KOH solution. The rate of this reaction depends upon the concentration of the compound ‘A’ only. When another optically active isomer ‘B’ of this compound was treated with aq. KOH solution, the rate of reaction was found to be dependent on the concentration of compound and KOH both. (i) Write down the structural formula of both compounds ‘A’ and ‘B’. (ii) Out of these two compounds, which one will be converted to the product with an inverted configuration.

Because the rate of reaction of compound ‘A' (C4H9Br) with aqueous KOH is solely determined by the concentration of compound ‘A,' the reaction happens via the SN1 mechanism, and product ‘A' is...

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Aryl chlorides and bromides can be easily prepared by electrophilic substitution of arenes with chlorine and bromine respectively in the presence of Lewis acid catalysts. But why does the preparation of aryl iodides requires the presence of an oxidising agent?

Arenes' iodination can be reversed due to the production of HI. An oxidising agent, such as HNO3 or HIO4, oxidises HI to speed up the process and stabilise the result.

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Ethylene chloride and ethylidene chloride are isomers. Identify the correct statements. (i) Both the compounds form the same product on treatment with alcoholic KOH. (ii) Both the compounds form the same product on treatment with aq.NaOH. (iii) Both the compounds form the same product on reduction. (iv) Both the compounds are optically active.

Option (i) and (iii) are the answers. They give ethyne on treatment with alcoholic $\mathrm{KOH}$. $ \mathrm{CH}_{3} \mathrm{CHCl}_{2} \underset{\mathrm{KOH}}{\stackrel{\text { alc....

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Which of the following statements are correct about the kinetics of this reaction? (i) The rate of reaction depends on the concentration of only (b). (ii) The rate of reaction depends on the concentration of both (a) and (b). (iii) Molecularity of reaction is one. (iv) Molecularity of reaction is two.

Option (i) and (iii) are the answers. The SN1 mechanism is used in the given reaction. The production of carbocation is a gradual process in the SN1 mechanism. As a result, the pace of reaction is...

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Which of the following statements are correct about the mechanism of this reaction? (i) A carbocation will be formed as an intermediate in the reaction. (ii) OH–will attach the substrate (b) from one side and Cl- will leave it simultaneously from the other side. (iii) An unstable intermediate will be formed in which OH– and Cl– will be attached by weak bonds. (iv) The reaction proceeds through an SN1 mechanism.

Option (i) and (iv) are the answers. Because it is a tertiary halide, it undergoes the SN1 process, resulting in the formation of a carbocation as an intermediate.  

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Which of the following statements are correct about the reaction intermediate? (i) Intermediate (c) is unstable because in this carbon is attached to 5 atoms. (ii) Intermediate (c) is unstable because carbon atom is sp2 hybridised. (iii) Intermediate (c) is stable because carbon atom is sp2 hybridised. (iv) Intermediate (c) is less stable than the reactant (b).

Option (i) and (iv) are the answers. Intermediate (iii) is unstable in the above reaction because the carbon atom is linked to 5 atoms and is less stable than reactant (ii).

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Which of the following statements are correct about this reaction? (i) The given reaction follows the SN2 mechanism. (ii) (b) and (d) have the opposite configuration. (iii) (b) and (d) have the same configuration. (iv) The given reaction follows the SN1 mechanism.

Option (i) and (ii) are the answers. Alkyl halide is the main reactant in the given reaction. A transient condition is found here, in which one bond is broken and another is created synchronously,...

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Which of the statements are correct about the above reaction? (i) (a) and (e) both are nucleophiles. (ii) In (c) carbon atom is sp3 hybridised. (iii) In (c) carbon atom is sp2 hybridised. (iv) (a) and (e) both are electrophiles.

Option (i) and (iii) are the answers. Nucleophiles are HO and CF. The C atom is sp2 hybridised in (iii) due to the simultaneous creation of the C – OH bond and the breakdown of the C – Cl link. As a...

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Which is the correct increasing order of boiling points of the following compounds? 1-Bromoethane, 1-Bromopropane, 1-Bromobutane, Bromobenzene (i) Bromobenzene < 1-Bromobutane < 1-Bromopropane < 1-Bromoethane (ii) Bromobenzene < 1-Bromoethane < 1-Bromopropane < 1-Bromobutane (iii) 1-Bromopropane < 1-Bromobutane < 1-Bromoethane < Bromobenzene (iv) 1-Bromoethane < 1-Bromopropane < 1-Bromobutane < Bromobenzene

Option (iv) is the answer Reason: As the molecular mass of the alkyl halide grows, the boiling point rises.

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Which is the correct increasing order of boiling points of the following compounds? 1-Iodobutane, 1-Bromobutane, 1-Chlorobutane, Butane (i) Butane < 1-Chlorobutane < 1-Bromobutane < 1-Iodobutane (ii) 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane < Butane (iii) Butane < 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane (iv) Butane < 1-Chlorobutane < 1-Iodobutane < 1-BromobutaneSolution:

Option (i) is the answer. Explanation: The larger the surface area, the stronger the intermolecular forces of attraction and, as a result, the higher the boiling point. For comparable types of alkyl...

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Toluene reacts with a halogen in the presence of iron (III) chloride giving ortho and para halo compounds. The reaction is (i) Electrophilic elimination reaction (ii) Electrophilic substitution reaction (iii) Free radical addition reaction (iv) Nucleophilic substitution reaction

Option (ii) is the answer. In the presence of Iron(III) chloride, toluene interacts with halogen to produce ortho and para halo compounds in an electrophilic substitution process. The Cl atom...

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Which of the following reagents can be used to oxidise primary alcohols to aldehydes? (i) CrO3 in an anhydrous medium. (ii) KMnO4 in acidic medium. (iii) Pyridinium chlorochromate. (iv) Heat in the presence of Cu at 573K

Option (i), (iii) and (iv) are the answers. Primary alcohols can be oxidised to aldehydes using CrO3 in an anhydrous media. CrO3 serves as an oxidizer in this situation. As a result, option I is the...

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Arrange the following compounds in increasing order of boiling point. Propan-1-ol, butan-1-ol, butan-2-ol, pentan-1-ol (i) Propan-1-ol, butan-2-ol, butan-1-ol, pentan-1-ol (ii) Propan-1-ol, butan-1-ol, butan-2-ol, pentan-1-ol (iii) Pentan-1-ol, butan-2-ol, butan-1-ol, propan-1-ol (iv) Pentan-1-ol, butan-1-ol, butan-2-ol, propan-1-ol

Option (i) is the answer As the moleculer mass of the alcohol grows, the boiling point rises. Furthermore, $1^0$ alcohols have greater boiling points than $2^0$ alcohols among isomeric alcohols.

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