# Class 12 NCERT Solutions

### Chemistry Chapter-01: The Solid State

Q1. What do you understand by amorphous solids ? Give examples.

Ans:

Amorphous solids are solids without a regular/ definitive arrangement of its constituent particles (ions, atoms or molecules) and they possess something called the short range order i.e., a regular and periodically repeating arrangement is seen only over short distances, e.g., rubber, glass.

### Chemistry Chapter-02: Solutions

Q 2.1) If 22 g of benzene is dissolved in 122 g of carbon tetrachloride, determine the mass percentage of carbon tetrachloride (CCl4) and benzene (C6H6).

### Chemistry Chapter-03: Electrochemistry

Q 3.1:

In the order of their reactivity, i.e how they displace each other from their salt solutions, allign the metals in decreasing order. Cu, Fe, Al, Zn and Mg.

### Chemistry Chapter-04: Chemical Kinetics

Q 1. Find out the rate of expression for the given reaction, also find the dimensions of the rate constant and their order of reaction.

(a) $$3\; NO(g) \rightarrow N_{2}O (g) \; Rate = k\left [ NO \right ]^{2}$$

(b) $$H_{2} O_{2} (aq) + 3I^{-}(aq) + 2H^{+} \rightarrow 2H_{2}O (I) + I^{-} \; Rate = k \left [ H^{2}O^{2} \right ]\left [ I^{-} \right ]$$

(c) $$CH_{3}CHO (g) \rightarrow CH_{4} (g) + CO (g) \; Rate = k\left [ CH_{3} CHO \right ]^{\frac{3}{2}}$$

(d) $$C_{2}H_{5}Cl (g) \rightarrow C_{2}H_{4} (g) + HCl (g) \; Rate = k\left [ C_{2} H_{5}Cl \right ]$$

### Chemistry Chapter-05: Surface Chemistry

Question 5.1: Differentiate between the phenomenon of adsorption and absorption.

Give one example for each.

### Chemistry Chapter-06: Isolation of Elements

Q1. Explain why hydro-metallurgy can extract copper , but cannot extract zinc.

### Chemistry Chapter-07: The p-Block Elements

Q 1:Briefly describe the general characteristics of Group 15 elements with reference to their oxidation state, electronic configuration, atomic size, electronegativity andionisation enthalpy.

### Chemistry Chapter-08: The d-and f-Block Elements

Q 8.1:

Write the electronic configuration of:

(i) Th4+ (ii) Lu2+ (iii) Ce4+ (iv) Pm3+ (v) Mn2+ (vi) Co2+ (vii) Cu+ (viii) Cr3++

### Chemistry Chapter-09: Coordination Compounds

Q1. Using Werner’s postulates describe the bonding present in coordination compounds.

### Chemistry Chapter-10: Haloalkanes and Haloarenes

Question 10.1: Name the following halides according to IUPAC system and classify them as alkyl, allyl, benzyl ( primary, secondary, tertiary ), vinyl or aryl halides :

### Chemistry Chapter-11: Alcohols, Phenols and Ethers

Q 11.1 :

Give IUPAC names of the compounds given below :

### Chemistry Chapter-12: Aldehydes, Ketones and Carboxylic Acids

Question 12.1: What do you mean by the following terms? Give an example of the reaction.

(i) Cyanohydrin

(ii) Acetal

(iii) Semicarbazone

(iv) Aldol

(v) Hemiacetal

### Chemistry Chapter-13: Amines

Q . 13.1 :

Give IUPAC names for the compounds given below & categorize them into primary, secondary & tertiary amines.

### Chemistry Chapter-14: Biomolecules

Q 1. Explain monosaccharide?

### Chemistry Chapter-15: Polymers

Q1: Define the following terms: monomer and polymer.

### Chemistry Chapter-16: Chemistry in Everyday Life

Question 1:

Why should we distinguish drugs in different ways?

### EXERCISE – 1.1

Q-1: Check each and every relation whether the following are symmetric, reflexive and transitive:

(i) The relation R of the set S = {2, 3, 4, 5, 6, 7, 8, 9. . . . . . . . 15} is defined as

R = {(a, b): 2a – b = 0}

### Exercise 2.1

Q1. Find principal value for $$\sin^{-1}\left ( -\frac{1}{2} \right )$$

Soln:

### EXERCISE – 3.1

Q-1: In a matrix given below:

A = $$\begin{bmatrix} 3 & 6 & 20 & -8 \\ 36 & -3 & \frac{ 7 }{ 2 } & 13 \\ \sqrt{ 5 } & 2 & -6 & 18 \end{bmatrix}$$, write

(a) the order of the matrix.

(b) the number of element.

(c) Write the elements of a13, a21, a23, a24, a33

### Exercise 4.1

Q1: Evaluate the determinants.

$$\begin{vmatrix} 2 & 4\\ -5 & -1 \end{vmatrix}$$

### Exercise 5.1

Q1: Prove that the function $$f(x)=5x-3$$ is continuous

at $$x=0$$, at $$x=-3$$ and at $$x=5$$.

Sol:

### Exercise 6.1

Q-1) For a circle, with radius given below, find the rate of change of the area w.r.t radius ’a’.

i) a = 2mm,

ii) a = 5mm

### Exercise – 7.1

Question 1:

By the method of inspection obtain an integral (or anti – derivative) of the sin 3x.

CASE – 1:

### Exercise: 9.1

Q.1: Find the degree and order of the differential equation $$\frac{\mathrm{d} ^{4}y}{\mathrm{d} x^{4}}$$+sin (ym) = 0.

### Exercise – 10.1

Question 1: Graphically represent a 40 km displacement towards 30 o east of north.

### Exercise 1.1

Q1. Find the cosine directions, if a line makes angles 90°, 135°, 45° with x, y and z- axes respectively.

### Exercise – 12.1

Q1: Maximize Z = 3x + 4y
Subject to the constraints: x + y ≤ 4, 0 ≤ x, 0 ≤ y

### Exercise – 13.1

Q.1: Q and R are events such as P(Q) = 0.6 , P(R) = 0.3, P($$Q\cap R$$) = 0.2. Determine the value of P($$\frac{Q}{R}$$) and P($$\frac{R}{Q})$$

Sol:

### Physics Chapter-01: Electric Charges and Fields

Q.1) Two small charged spheres having charges of 2 x 10-7C and 3 x 10-7C are placed 30 cm apart in air. What will be the force between these two charges?

### Physics Chapter-02: Electrostatic Potential and Capacitance

Q.1) 5 × 10-8 C and -3 x 10-8 C are the two charges located 16 cm apart from each other. At what point(s) between these two charges the electric potential is zero?

Soln.: Given,

### Physics Chapter-03: Current Electricity

Question 3.1:

Car has a storage battery with an emf of 12 V. 0.4Ω is the internal resistance of the battery

, what is the maximum current that can be drawn from the battery?

### Physics Chapter-04: Moving Charges and Magnetism

Q 4.1) Determine the magnitude of the magnetic field B at the centre of the circular coil of wire carrying current of 0.4 A and having 100 turns with 8 cm being the radius of each turn.

### Physics Chapter-05: Magnetism and Matter

(a) The specification of a vector requires 3 quantities. What are the three quantities that are independent and can be used conventionally to determine the earth’s magnetic field?

(b) Will the dip angle be greater or smaller in Britain, if $$18°$$ is the dip angle at a location in southern India?

### Physics Chapter-06: Electromagnetic Induction

Q 1. From the given figure determine the direction of the current induced in the different given situations.

### Physics Chapter-07: Alternating Current

Question 7.1 :

A resistor of 100 Ω is being connected to a supply of 220 V, 50 Hz

(a) Calculate the rms value of current in the connection

(b) Calculate the total power being consumed over an entire cycle

### Physics Chapter-08: Electromagnetic Waves

Q 8.1) Two circular plates having radius of 12 cm each and separated by 5 cm are used to make a capacitor as shown in the Figure 8.6. An external source charges this capacitor. 0.15 A is the charging current which remains constant.

(a) Determine the capacitance and the rate of charge of potential difference between the two capacitiveplates.

### Physics Chapter-09: Ray Optics and Optical Instruments

Question 1:

A candle which is 2.5 cm in height is placed 27cm in front of a concave mirror having radius of curvature 36 cm. Find the distance from the mirror at which the screen should be placed to obtain a sharp image? Detail the size and nature of the image.

By how much the screen have to be moved if the candle is moved towards the mirror?

### Physics Chapter-10: Wave Optics

Question 1:

Monochromatic light having a wavelength of 589nm from the air is incident on a water surface. Find the frequency, wavelength and speed of (i) reflected and (ii) refracted light? [1.33 is the Refractive index of water]

### Physics Chapter-11: Dual Nature of Radiation and Matter

Q.11.1: Find the:

(a) Maximum frequency, and

(b) The minimum wavelength of X-rays produced by 30 kV electrons.

### Physics Chapter-12: Atoms

Q1: Pick an appropriate option to justify the given statement:

(a) Size of an atom in Rutherford’s model is _________ the size of an atom compared to of Thomson’s model. (Less than, Greater than, no different than)

### Physics Chapter-13: Nuclei

Q 13.1 (a) Lithium has two stable isotopes $$_{3}^{6}\textrm{Li}$$ and $$_{3}^{7}\textrm{Li}$$ have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.

(b) Two stable isotopes of Boron , $$_{5}^{10}\textrm{B}$$ and $$_{5}^{11}\textrm{B}$$ . Their respective masses are 10.01294 u and 11.00931 u, and the atomic mass of boron is 10.811 u. Find the abundances of $$_{5}^{10}\textrm{B}$$ and $$_{5}^{11}\textrm{B}$$.

### Physics Chapter-14: Semiconductor Electronics

Q 1. Find which of the given statement is true for an n – type silicon.

(a) Majority carriers are the electrons and dopants are the trivalent.

(b) Minority carriers are the electrons and dopants are the pentavalents.

(c) Minority carriers are the holes and dopants are the pentavalent.

(d) Majority carriers are the holes and dopants are the trivalent.

### Physics Chapter-15: Communication Systems

Q.1: For beyond – the – horizon communication, which of the following frequencies will be suitable using sky waves?

(1) 10 kHz

(2) 10 MHz

(3) 1 GHz

(4) 1000 GHz