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Physics & Chemistry Test 3
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Physics & Chemistry Test 3
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  • Question 1/30
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    The property of carbon atom to bond with other atoms of carbon giving rise to long chains of carbons is known as:
    Solutions

    Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called as catenation.

    These compounds may have long chains of carbon, branched chains of carbon or even carbon atoms arranged in rings

    Figure:

  • Question 2/30
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     If the acceleration due to gravity on the surface of the earth is g, then the acceleration due to gravity on the surface of a planet whose mass is half of that of earth and radius is same as that of the earth is _________.

    Solutions

    If the acceleration due to gravity on the surface of the earth is g, then the acceleration due to gravity on the surface of a planet whose mass is half of that of earth and radius is same as that of the earth is g/2.

    Formula for acceleration due to gravity =

    Where, G = Newton's gravitational constant = 6.67 × 10-11 N m2/kg2.

    m = mass of the Earth and r = radius of the Earth.

    Let us take m1 as the mass of the planet which is half of that of the Earth and g1 is its acceleration due to gravity.

    Now g1 = .

    Putting m1 as , we get,

    g1

    Thus, it proves that if the acceleration due to gravity on the surface of the earth is g, then the acceleration due to gravity on the surface of a planet whose mass is half of that of earth and radius is same as that of the earth is .

  • Question 3/30
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    Which of the following is law of chemical combination?
    Solutions

    There are two laws of chemical combination:

    Law of conservation of mass

    Law of conservation of mass states that in a chemical reaction mass can neither be created nor destroyed.

    Law of constant proportion

    In a chemical substance the elements are always present in definite proportions by mass.
  • Question 4/30
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    When lead nitrate is heated, the brown fumes observed are of:
    Solutions

    Heating of lead nitrate is an example of decomposition reaction:

    The brown fumes observed are of Nitrogen Dioxide (NO2)

    Point to Note:

    Identification of gases in chemistry can be done as below:

    Gas

    Characteristics

    Hydrogen

    Burns with a popping sound

    Oxygen

    Glowing wooden splint relights in a test tube of oxygen

    Carbon dioxide

    Turns limewater milky

    Ammonia

    Characteristic sharp, choking smell

    Chlorine

    Characteristic sharp, choking smell. It makes damp blue litmus paper turn red

  • Question 5/30
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    A fuse wire should have
    Solutions

    The material used for fuse elements must be of low melting point, low ohmic loss, high resistance, low cost and free from detraction.

    The material used for making fuse element has a low melting point such as tin, lead, or zinc.
  • Question 6/30
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    Let “t” be the time during which a charge “Q” flows through a resistor R having potential difference V across its ends. The power dissipated is given by:
    Solutions

    The power dissipated in conductor is given by

    P = VI      ----(1)

    Current I through the conductor is related to charge Q by the relation

            ----(2)

    Substituting in (1)

  • Question 7/30
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    Which part of human ear converts sound vibrations into electrical signals
    Solutions

    The vibrations are amplified several times by three bones (the hammer, anvil and stirrup) in the middle ear.

    The middle ear transmits the amplified pressure variations received from the sound wave to the inner ear.

    In the inner ear, the pressure variations are turned into electrical signals by the cochlea.

    These electrical signals are sent to the brain via the auditory nerve, and the brain interprets them as sound.

  • Question 8/30
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    Calcium oxide reacts with water to form calcium Hydroxide. Which type of reaction is this?
    Solutions

    Concept:

    Combination Reaction:

    A combination reaction (also known as a synthesis reaction) is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product).

    Such reactions may be represented by equations of the following form:

    X + Y → XY

    Combination reactions are usually exothermic because when the bond forms between the reactants, heat is released

    Exothermic Reaction:

    During a reaction if heat is released, then the reaction is known as exothermic reaction.

    Endothermic Reaction:

    During a reaction if heat is absorbed from the surrounding then reaction is known as Endothermic reaction.

    Application:

    The given reaction can be written as

  • Question 9/30
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    Isotopes of an element have
    Solutions

    The elements having the same atomic number, but a different mass number are referred to as isotopes.

    The total number of protons and neutrons in the nucleus is the atom's mass number.

    The atomic number is the number of protons found in the nucleus of an atom.

    Isotopes have same chemical properties.

  • Question 10/30
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    If the following equation is balanced, the value of “b” is:

    a Al + b HCl → c AlCl3 + d H2
    Solutions

    First balance the chlorine

    Al + 3 HCl → AlCl3 + H2

    Next balance the hydrogen

    Multiply the whole equation by 2 to get integer coefficients

  • Question 11/30
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    Which of the following is the correct order of reactivity of metals?
    Solutions

    The reactivity series of metals is given below:

    From the table correct order of reactivity is

    Al > Zn > Fe

    Trick to remember:

    Kedar Nath Ca Mali Aloo Zara Fike Sne Pkata Hai Cyuki Har taraf Alag Auloo Pdta hai

    1) Kedar - K - Potassium

    2) Nath - Na - Sodium

    3) Ca - Ca - Calcium

    4) Mali - Mg - Magnesium

    5) Aloo - Al - Aluminium

    6) Zara - Zn - Zinc

    7) Fike - Fe - Iron

    8) Se - Sn - Tin

    9) Pkata - Pb - Lead

    10) Hai - H - Hydrogen

    11) Cyuki - Cu - Copper

    12) Har - Hg - Mercury

    13) Alag - Ag - Silver

    14) Auloo - Au - Gold

    15) Pdta - Pt – Platinum

  • Question 12/30
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    Current flows due north in a horizontal transmission line. Magnetic field at a point vertically above it, is directed

    Solutions

    By using right hand thumb rule or any other rule which helps to determine the direction of magnetic field.

  • Question 13/30
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    Which would require a greater force accelerating a body A with 2 kg mass at 5 m/s2 or a body B with 5 kg mass at 2 m/s2
    Solutions

    The force required to accelerate a body of mass “m” with acceleration “a” is given by:

    F = ma

    For Body A

    F = 2(5)

    F = 10 N

    For Body B

    F = 5(2)

    F = 10 N

    Hence both bodies require same effort/force.
  • Question 14/30
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    Light enters the eye through a transparent membrane known as
    Solutions

    The cornea is the transparent membrane from where the light enters the human eye.

    Different parts of the eyes and their functions are shown in the table:

    Name of the Part

    Characteristics

    Function

    Cornea

    The transparent spherical membrane covering the front part of the eye

    Light enters the eye through this membrane; Most of the refraction happens here

    Eye Lens

    transparent, biconvex structure in the eye

    provides finer adjustment required to focus objects on the retina

    Iris

    Dark muscular diaphragm between the cornea and the lens

    controls the size of the pupil

    Pupil

    An opening between the iris through which light enters the eye

    regulates the amount of light entering the eye

    Ciliary Muscles

    Attached to the eye lens


    hold the lens in position and modify the curvature of the lens.

     

    Retina

    a light-sensitive surface of an eye on which the image is formed

    generate signals which are transmitted to the brain through optical nerves

    Optic Nerve

    Attached to retina

    transmits visual information from the retina to the brain

  • Question 15/30
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    In a homologous series of as the molecular mass increases which of the following statements is true:

    Solutions
    • As the molecular mass increases in any homologous series, a gradation in physical properties is seen
    • This is because the melting points and boiling points increase with increasing molecular mass
    • Physical properties such as solubility in a particular solvent show a similar gradation
    • The chemical properties, which are determined only by the functional group, remain similar in a homologous series

    Trick:

    Physical properties are function of Molecular mass

    Chemical Properties are function of functional groups such as alcohol, ketone, aldehyde etc.

  • Question 16/30
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    The substances whose odour changes in acidic or basic media are called:
    Solutions
    • The substances whose odour changes in acidic or basic media are called Olfactory Indicators
    • Onion, Clove, Vanilla etc. are some examples of Olfactory Indicators
    • These are the type of indicators are found naturally and used to test whether a given solution is an acid or a base
    • Some common examples are turmeric, grape juice etc.
    • Synthetic indicators are different from natural indicators as the test for acids and bases is done with synthetic materials such as methyl orange and phenolphthalein
    • Any substance that indicates the presence of Acid or Base usually by changing colour is called Acid-base indicators
    • Some common examples are red cabbage leaves, Turmeric etc.
  • Question 17/30
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    A rider on horseback falls back when the horse starts running suddenly is because:
    Solutions

    Newton’s first law of motion:

    A body at rest continues to be at rest and a body in motion continues to be in motion with uniform velocity along a straight line unless an external unbalanced force acts on it to change its position of rest or motion.

    In case of rider, the lower part of the body is initially at rest. As the horse starts moving the lower body comes in motion while the upper body still maintains its inertia of rest.

    As a result, the rider tends to fall back.
  • Question 18/30
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    Atomic mass unit is defined in terms of which of the following?
    Solutions
    • Atomic mass unit is defined in terms of carbon-12 (C-12).
    • The atomic mass unit is used to express atomic and molecular weights and it is equal to one-twelfth of the mass of the one C-12 atom.
    • The atomic weight of the hydrogen atom is used to compare the atomic weight of other elements.
    • N-15 is the non-radioactive, stable isotope of nitrogen. N-13, N-14, N-15, etc. are the other isotopes of nitrogen.
    • C-14 is an radioactive isotope of carbon used in carbon dating (determining the age of carbonaceous materials). C-12, C-13, and C-14 are the isotopes of carbon.
  • Question 19/30
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    Two bodies A and B have velocities in the ratio of 2: 1. Mass of body A is half of the mass of body B. The kinetic energy of A and B are in the ratio of
    Solutions

    Kinetic energy = (1/2) m v2

    Let the mass of body A be 'm' and therefore the mass of body B will be '2m'

    Same way, let the velocity of body A be '2v' and that of body B be 'v'

    KEa : KEb = (1/2) m (2v)2 : (1/2) (2m) v2

    KEa : KEb = 4mv2 : 2mv2

    KEa : KEb = 2 : 1

  • Question 20/30
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    Which one of the following is Dobereiner’s triad?
    Solutions

    According to this triad, when elements are arranged in order of their increasing atomic mass, the atomic mass of the middle element is approximately the arithmetic mean of the other two elements of the triad.

    Following are some of the examples Dobereiner’s triad.

    Li, Be and K

    C, N and O

    Ca, Sr and Ba

    Cl, Br and I

  • Question 21/30
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    Which of the following is common in all acids?
    Solutions
    • The Hydrogen present in acids is responsible for their acidic behaviour
    • An acidic substance donates its H+ ions in aqueous solution which causes imbalance of H+ and OH- ions concentration and make the overall solution acidic

    Basic:

    • The Hydroxide ions present in bases is responsible for their basic behaviour
    • A basic substance donates its OH- ions in aqueous solution which causes imbalance of H+ and OH- ions concentration and make the overall solution basic
  • Question 22/30
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    In Modern Periodic Table, the atomic radius increases ________.
    Solutions
    • In the Modern Periodic Table, the atomic radius increases while moving from right to left in a period.
    • Atomic radius decreases from left to right within a period. This is caused by the increase in the number of protons and electrons beyond a period.
    • One proton has a greater effect than one electron, thus, electrons are pulled towards the nucleus, which results in a smaller radius.
  • Question 23/30
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    If the reading of ammeter is 2 A then reading of voltmeter is:

    Solutions

    Current through upper 5Ω resistor is 2A

    Voltage drop across upper 5 Ω is 5(2) = 10 V

    Since all the resistors are in parallel the voltage across each of them is equal

    Voltmeter reading is 10 Volts
  • Question 24/30
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    The force of gravitation between two bodies of mass 1 kg each kept at a distance of 1 m is:
    Solutions

    The gravitational force between two bodies is given by:

    When m1 = m2 = 1 Kg

    And r = 1m

    6.67 x 10-11 Newton
  • Question 25/30
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    Which of the following will turn blue litmus red?
    Solutions

    Litmus test is done to identify the nature a substance.

    An acidic substance turns blue litmus red whereas a basic substance turns red litmus blue.

    Substance

    Nature

    Litmus Test

    Vinegar

    Acidic

    Blue Litmus Red

    Lime Water

    Basic

    Red Litmus Blue

    Baking Soda Solution

    Basic

    Red Litmus Blue

    Washing Soda Solution

    Basic

    Red Litmus Blue

     

    Common Confusion Point:

     A student may consider lime water as acidic but lime water is a saturated solution of a base called calcium hydroxide (chemical formula Ca(OH)2) in water. Hence, lime water is not acidic but basic in nature.

    Lime juice is the juice obtained from lime, a citrus fruit. This contains citric acid and is therefore sour in taste and is acidic in nature.
  • Question 26/30
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    A body is thrown vertically upward with velocity u, the greatest height ‘h’ to which it will rise is:
    Solutions

    Concept:

    3 equations of motion govern the position of any particle:



    Application of Concept:

    When the body is thrown upwards, at the top most point its final velocity becomes zero

    Using third equation of motion

    v = 0

    a = -g

  • Question 27/30
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    A particle is moving in a circular path of radius r, the displacement after half a circle would be:
    Solutions

    Displacement of an object is defined as the shortest distance between the initial and final position of the particle:

    If an object starts from A and travels semicircular path till B

    The shortest distance between the initial and final position is given by the diameter of the semicircle.

    Diameter = 2r

  • Question 28/30
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    A concave lens has focal length of 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens?
    Solutions

    A concave lens always forms a virtual, erect image on the same side of the object.

    Image-distance v = –10 cm;

    Focal length f = –15 cm;

    Object-distance u = ?

    Since 
    1/v - 1/u = 1/f

    or,
    1/u = 1/v - 1/f
    Putting the values,

    u = -30 cm

    Thus, the object-distance is 30 cm. 

  • Question 29/30
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    The total energy of freely falling object:
    Solutions
    • Under free fall where gravity is the sole influence on the body, the total energy remains the same
    • Potential energy gets converted into the kinetic energy
    • Potential Energy keeps on decreasing and kinetic energy keeps on increasing
    • This is also in confirmation with the law of conservation of energy
  • Question 30/30
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    Which of the following metal oxide is amphoteric in nature?
    Solutions

    Basic Knowledge:

    Metal oxides are basic in nature and non-metallic oxides are acidic in nature.

    Some Metal oxides such as Aluminium oxide, Zinc oxide etc. are both acidic as well as basic in nature. Such metal oxides react with both acids as well as base to produce salt and water.

    These oxides are known as amphoteric oxides.

    Underlying Reactions:

    Reaction with acid

    Reaction with base

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