Madhyamik physical science Question Paper 2018 Solve

WB Madhyamik physical science Solve

Madhyamik Pariksha 2018 Solve- physical science

SUBJECT: physical science Year: 2018

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Group A

1. Multiple choice questions. Four alternatives are given as answers for each of the following questions. Write the correct one.

1.1 Which of the following greenhouse gases has the maximum contribution towards global warming?

(a) N₂O

(b) CH₄

(c) CO₂

(d) H₂O vapor

Ans.(c) CO₂

1.2 According to Boyle’s law what is the PV-P graph?

1.3 If the vapor density of a carbon-containing gaseous substance is 13, which of the following can be its molecular formula?

(a) CO₂ (b) C₂H₄ (c) C₂H₆ (d) C₂H₂

Ans. (d) C₂H₂

1.4 The unit of coefficient of linear expansion of a solid is-

(a) m (b) m^-1 (c) °C^-1 (d) °C

Ans. (c) °C^-1

1.5 An object is placed in between the optical center and the focus of a thin convex lens. What is the nature of the image of the object?

(a) real and inverted

(b) virtual and inverted

(d) virtual and erect

Ans. (d) virtual and erect

1.6 When a ray of light is incident perpendicularly on a transparent glass slab, what will be its angle of deviation?

(a) 0° (b) 180° (c) 30° (d) 90°

Ans.(a) 0°

1.7 Which of the units given below is the SI unit of resistance?

(a) volt

(b) ampere

(d) ohm

Ans. (d) ohm

1.8 In a domestic electric circuit the fuse wire is connected to which of the following?

(a) Earth line

(b) live line

(d) the both live and neutral line

Ans. (b) live line

1.9 B-ray emitted from a radioactive element is

(a) a stream of electrons

(b) a stream of protons

(d) electromagnetic wave

Ans. (a) a stream of electrons

1.10 How many groups are there in the long periodic table?

(a) 7 (b) 8 (c) 9 (d) 18

Ans.(d) 18

1.11 In the formation of which of the following compounds octet rule is not obeyed?

(a) NaCl (b) LiH (c) KCI (d) CaO

Ans.(b) LiH

1.12 Which of the following can conduct electricity?

(a) (molten) NaCl

(b) (liquid) HC1

(d) (aqueous solution of glucose)

Ans.(a) (molten) NaCl

1.13 What will be the color of the resulting solution when excess aqueous ammonia is added to an aqueous solution of copper sulfate

(a) yellow

(b) green

(d) brown

Ans.(c) deep blue

1.14 In which of the following alloys zinc is present?

(a) bell metal

(b) brass

(d) duralumin

Ans. (b) brass

1.15 Which of the following is a saturated hydrocarbon?

(a) C₃H₆ (b) C₂H₄ (c) C₂H₂ (d) C₂H₆

Ans.(d) C₂H₆

Group ‘B’

1. Answer the following questions (Alternatives are to be noted)
2.1 Mention one use of biogas.

Ans. Vaio gas is used as fuel and for lighting, it is smokeless.

OR, what is the role of NO in the decomposition of ozone in the ozone layer?

2.2 Among charcoal, petrol, and ethanol which one is a fossil fuel?

Ans. petrol.

2.3 Under constant pressure, at what temperature in degrees Celsius the volume of an ideal gas will be zero according to Charles’ law?

Ans. The volume of an ideal gas becomes zero at -273°C (at absolute zero temperature).

2.4 What is the unit of M in the equation PV = w/M RT? (The meaning of the signs)

Ans. The unit of M is gram/mol or gm mol-¹ in the C.G.S system and S.I. in kg mol-¹.

2.5 Whether the following statement is ‘true’ or ‘false’?

The real expansion of any liquid depends on the expansion of the vessel in which it is kept.

Ans. true

OR, Among iron. Invar, and copper which one has the least coefficient of linear expansion?

Ans. The linear expansion coefficient of alloy invar is less than that of iron and copper.

2.6 Between the angle of incidence and the angle of refraction which one is greater when light travels from a rarer to a denser medium?

Ans. When a ray of light passes from a rarer to a denser medium, the angle of incidence is greater than the angle of incidence.

2.7 What type of mirror is used in the viewfinder of a motor car?

Ans. Convex Mirror

2.8 How does the resistance of a semiconductor change with the increase in temperature?

Ans. The resistance of a semiconductor decreases with an increase in temperature.

2.9 Which type of energy is transformed into electrical energy in a dynamo?

Ans. Mechanical energy is converted into electrical energy in dynamos.

2.10 Arrange a, P, and y-rays in ascending order of their penetrating power.

Ans. a< B<y

OR, which kind of nuclear reaction is the source of the sun’s energy?

Ans. The source of the Sun’s energy is the process of nuclear fission.

2.11 Match the right column with the left column:

Left column                                                                           Right column

2.11.1 An alkali metal                                                           (a) F

2.11.2 An element whose anion accelerates rusting of iron       (b) Fe

2.11.3 Extracted from hematite                                           (c) K

2.11.4 Most electronegative element                                              (d) Cl

Ans. 2.11.1-(c) K, 2.11.2-(d) Cl, 2.11.3-(C) Fe, 2.11.4-(C) F.

2.12 What type of chemical bond is present in CaO?

Ans. Cao has electronegative bonding.

2.13 What is used as a cathode to electroplate silver over a copper spoon?

Ans. Copper spoon at the cathode.

OR, the example of a compound whose aqueous solution is a weak electrolyte.

Ans. Ammonia hydroxide (NH₄OH) or hydrogen cyanide (HCN) or acetic acid (NH₃COOH), NH₃ (ammonia), etc. are weak electronegative.

2.14 During electrolysis which electrode is called a cathode?

Ans. In electrochemical analysis, the cathode from which the current flows out and the metal on which the electroplating is applied is the cathode.

2.15 State one use of liquid ammonia.

Ans. Liquid ammonia is used to clean ceramic and steel utensils.

OR, Write the formula of the precipitate formed when an aqueous ammonia solution is added to an aqueous solution of aluminum chloride.

Ans. On mixing an aqueous solution of ammonia with an aqueous solution of aluminum chloride, aluminum

A brown-colored precipitate of hydroxide (Al (OH)₃) is obtained.

AICI₃ (Aq) + 3 NH₄OH (Aq) = 3 NH₄C/ (Aq) + A/ (OH)₃ ↓

2.16 In the laboratory preparation of nitrogen, aqueous solution of which compound is mixed with the aqueous solution of ammonium chloride and heated?

Ans. In the laboratory, nitrogen gas is prepared by heating a mixture of a concentrated solution of ammonium chloride and sodium nitrite.

2.17 Write the IUPAC name of CH₃, CH₂, and CHO.

Ans. The IUPAC name for CH₃, CH₂, CHO is Protanal.

OR, Write the structural formula of the positional isomer of CH₃, CH₂, CH₂, OH.

Ans. The structural formula of position isomer CH₃, CH₂, CH₂, OH

2.18 Mention one use of poly (tetrafluoroethylene

Ans. In making shoes, slippers, buckets, etc., and non-stick cookware sets are made from it, in which oil, ghee, etc. do not stick. Apart from this, gaskets, beads, etc. are made.

Group C

1. Answer the following questions (Alternatives are to be noted):
3.1 What is methane hydrate?

Ans. Methane hydrate: – These new and clean hydrocarbons are attracting the attention of scientists as an enersourcesrce. These are known as flammable ice. These are distributed throughout the world in the permafrost sediments of the Arctic and on the continental boundary at depths of 500 m. Methane and some other gases combine with water at appropriate pressure and temperature to form it. They are like ice in appearance, which, when brought to normal temperature and pressure, releases methane gas. This gas can be used as an energy source.

3.2 The pressure of a fixed mass of a gas at a temperature of 0°C is doubled while the volume is halved. What will be the final temperature of the gas?

Ans.

OR, under constant pressure, a fixed mass of a gas is heated from 0°C to 546°C. What is the ratio of the final volume of the gas to its initial volume?

Ans.

3.3 What is meant by the optical center of a convex lens?

Ans. Optical center: – The point on the principal axis in the middle of the lens through which the rays of light pass through do not change their direction while emerging from the second plane of the lens after reverberation. Hence O is the center of light of the lens.

Or why does the earth’s sky appear blue during the daytime?

Ans. The reason why the color of the sky appears blue: – When sunlight passes through the atmosphere, it is scattered by the molecules of gases, water drops, dust particles, etc. The smallest of these particles are the gas molecules which scatter the blue color more. This scattered light reaches our eyes and that is why the sky appears blue to us.

3.4 State Lenz’s law related to electromagnetic induction.

Ans. Lenz’s Law: In the event of electromagnetic induction, the induced emf and the direction of the induced current are determined by Lenz’s law. According to this law, the direction of the induced current in a circuit in all cases due to electromagnetic induction is such that it opposes the cause due to which it, i.e., the induced current itself, arises. (The direction of the induced current is such that it opposes the cause which induces it)

3.5 Write with an example of how according to Lewis’s concept a covalent bond is formed.

Ans. According to Lewis, “If all the atoms participating in a reaction are of equal charge and are isomorphic, then such atoms share their outermost electron in the reaction. This sharing results in the formation of a pair of electrons which may be one or more. Both the repulsors, by treating this pair equally, acquire stability by obtaining the electron configuration of their nearest inactive element. At this time the nuclear nucleus remains unaffected.

Example: Formation of a molecule of methane (CH4) – A molecule of methane is formed by a covalent bond between one atom of carbon and four atoms of hydrogen.

Or why the bond in sodium chloride cannot be expressed as Na-CI?

Ans. The sodium ion has a cubic charge and the chloride ion has a negative charge, these opposite ions combine by an electromotive force to form

sodium chloride Na + Cl – or NaCl.

In solid sodium chloride, as Rava, opposite charges are held together. There should be an equal number of sodium chloride (Na +) n (Cl-)n or (Na +C1-) n where n is a larger number. Hence it cannot be represented as Na – Cl. The simplest formula for sodium chloride is NaCl.

3.6 Give one example each of a liquid and a solid covalent compound.

Ans. Liquid covalent compounds are alcohol, and water (H₂O) and solid covalent compounds are sugar, naphthalene, etc.

3.7 Write with a balanced chemical equation what happens when H₂S gas is passed through an aqueous copper sulfate solution.

Ans. On passing H2S gas in an aqueous solution of copper sulfate, a black-colored precipitate of cupric sulfide (CuS) is obtained and an odorant is produced.

CuSO₄ + H₂S → H₂SO₄ + CuS

3.8 Write down the cathode reaction when an aqueous solution of MSO, (M=metal) is electrolyzed. Write with reason whether the reaction is oxidation or reduction.

Ans.

OR, Give one use of each of copper and aluminum.

Ans. Copper is used to making utensils. Aluminum is used for making household utensils and electrical wires.

3.9 What is the condition of the f substitution reaction of methane with chlorine? Write the balanced chemical equation of the first step of the reaction.

Ans. Substitution reaction of chlorine with methane reacts with chlorine when a mixture of methane and chlorine is exposed to sunlight. In this, the four hydrogen atoms of methane are replaced one by one by the chlorine atom. Such a reaction is called a substitution reaction.

CH₄ +CL₂ → CH₃CI + HCI.

Or Write with a balanced chemical equation what happens when ethanol reacts with metallic sodium.

Group D

4. Answer the following questions (Alternatives are to be noted):

4.1 Establish the ideal gas equation based on Boyle’s law, Charles’ law, and Avogadro’s law.

4.2 How many grams of Fes, is required for the production of 512 g of SO2) (Fe = 56, S = 32, 0=16)

By heating 200 g of a metal carbonate, 112gof metal oxide and gaseous compound are produced. The Vapor density of the gaseous compound is 22. How many moles of the gaseous compadres are produced in the reaction?

4.3 What is thermal conductivity? What is its SI unit?

or,

Define the coefficient of surface expansion. Write its SI unit.

4.4 How can an erect and magnified image be formed with the help of a convex lens? With the help of which type of lens long-sightedness can be rectified?

4.5 If the velocity of light in a medium is 2×10⁸ m/s, what will be the refractive index of that medium?

or,

the refractive index of a medium concerning air is √2 If the angle of incidence of a ray of light in air is 45° determine the angle of deviation for that ray in case of refraction.

4.6 State Joule’s laws of heating effect of current?

4.7 Calculate the equivalent resistance when a wire of resistance 10 ohms is divided into two equal parts and connected in parallel combination.

or,

there are two 60-watt lamps and two 80-watt fans in a house. The lamps and fans run for 5 hours daily. Find out the expense in a month if a unit of electricity costs Rs. 4/-. (Assume one month • 30 days)

4.8 Compare the charge and ionizing power of t – and y-rays. Mention one use of radioactivity.

or,

What is meant by the ionization energy of an atom of an element? Arrange Li, Rb, K, and Na in the increasing order of their ionization energy.

4.9 Why hydrogen is placed in group 1 and group 17? Give two points for justification.

4.10 State Lenz’s law related to electromagnetic induction and hence prove that this law is by laws of conservation of energy.

4.11 Write the conditions and balanced chemical equation for the industrial production of ammonia by Haber’s process.

4.12 The molecular formula of an organic compound is C₂ H_4’ and O₂. The compound is soluble in water and the addition of NaHCO₃ to the aqueous solution of the compound CO₂ evolved. Identify the organic compound. Write, with conditions and balanced chemical action, the reaction of the compound with ethanol.

Write the differences between organic and inorganic compounds.