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Physical Science Solution–2020

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1. Multiple choice question.
1.1 Which among the following gases does not help in the depletion of the ozone layer?
(a) NO
(b) NO2
(c) CFC
(d) CO2

1.2 What is the value of PV for 11.2 litre of an ideal gas at STP?
(a) 2 RT
(b) RT
(c) 0.5 RT
(d)11.2 RT

1.3 According to the following chemical equation CH4 + 2O2 CO2 + 2H2O What volume of O2 will be required to burn 10 mole of CH4 at STP?
(a) 448L
(b) 224L
(c) 44.8L
(d) 22.4L

1.4 Which among the following substances has the highest heat conductivity?
(a) Silver
(c) Copper
(d) Aluminium

1.5 If a beam of red light and a beam of violet light are incident at the same angle on the inclined surface of a prism from air medium and produce angles of refraction r and v respectively, which of the following is correct?
(a) r = v
(b) r = 1/v
(c) r > v
(d) r < v

1.6 A point source of light is placed at the centre of curvature of a concave mirror. The angle of deviation of the rays incident on the mirror from it source and reflected from it, is
(a) 0°
(b) 180
(c) 90°
(d) 360°

1.7 Coulomb’s law related to electric charges is applicable when of the two charges
(a) one is the point, one is spherical
(b) both are spherical
(c) one is the point, one is extended
(d) both are points

1.8 The characteristics of a fuse wire are
(a) high resistance, high melting point
(b) low resistance, low melting point
(c) low resistance, high melting point
(d) high resistance, low melting point

1.9 Present in α- particle
(a) one proton, one neutron
(b) one proton
(c) two protons, two neutron
(d) one electron

1.10 Which of the following is not a periodic property of elements?
(a) density
(b) melting point
(c) boiling point
(d) radioactivity

1.11 In which of the following compounds there is no existence of molecules?
(a) Hydrogen chloride
(b) Calcium oxide
(c) Methane
(d) Ammonia

1.12 Which of the following statements is correct in the case of electrolysis of CuSO4 solution using Cu electrodes?
(a) the mass of the cathode decreases
(b) the mass of the anode increases
(c) the concentration of CuSO4 in solution decreases
(d) the concentration of CuSO4 in solution remains unchanged

1.13 What color is produced when H2S gas is passed through an alkaline aqueous solution of sodium nitroprusside?
(a) violet
(b) orange
(c) deep blue
(d) green

1.14 The formula of red haematite, an ore of iron, is
(a) FeO
(b) Fe2 O3
(c) Fe3O4
(d) FeCO3

1.15 By the reaction of aqueous NaHCO3 with which of the following compounds CO2 is produced
(a) CH3CH2OH
(b) CH3CHO


2. Answer the following question (alternatives are to be noted).
2.1 Which fuel gas is harvested from coal-bed?
Or, Name a gas present in air, the increase in amount of which cause global warming

2.2 Name an energy source which can be used for sustainable development.

2.3 State whether the following statement is true or false.
The speed of the gas molecules contained in a closed vessel at fixed temperature and pressure is the same.

2.4 What is the nature of V versus T graph according to Charles’ law?

2.5 Whether the following statement is true or false?
Among copper, invar and iron the linear exposition coefficient of iron is the lowest.
Or, What is the unit of volume expansion coefficient?

2.6 What is meant by the pole of a spherical mirror?

2.7 Write down one use of x-ray.

2.8 Name a machine where electrical energy is converted to mechanical energy.

2.9 A part from the live wire, what are the two other wires in the household circuit?

2.10 Which kind of nuclear reaction produces energy in a nuclear reactor?
Or, Give an example of a natural radioactive element.

2.11 Match the right column with the left column:

Left ColumnRight Column
2.11.1) A transuranic elementa)Krypton
2.11.2) A noble elementb)Neptunium
2.11.3) Prepared by carbon reduction of the oxide
of the metal
2.11.4) In the alloy brass, the metal whose percentage
ammount is higher than that of the other metals

2.12 Between chloroform and sodium chloric which is not soluble in water ?
2.13 Name a metal which is extracted by the process of electrolysis.
Or, Which is the anode in the electroplating of silver on brass spoon?
2.14 Which energy causes chemical reaction during electrolysis?
2.15 Show by the help of appropriate litmus paper that the aqueous solution of ammonia is alkaline in nature.
Fill up the blanks:
NaOH + H2S _____ + H2O
2.16 Write one use of urea.
2.17 Write the structure formula of propanone.
Or, Wohler first prepared an organic compound from an inorganic compound in the laboratory. What is the organ compound?
2.18 Give an example of biodegradable natural polymer.


3. Answer the following questions.
3.1 Write with reason in which layer among the layers of the atmosphere the pressure is the highest.
Ans: Troposphere because the air density decreases as the altitude increases.

3.2 Find out the ratio of the volumes occupied by 32g O2 44g CO2 gases at 27°C temperature and 700mm Hg pressure. (C=12,0=60)
Ans: at constant temperature and pressure, volume of gas in the container is directly proportional to number of molecules present in the container.
i.e.., V x n
=> V1/V2 = n1/n2 where V is volume of gas and n is no of moles.
given mass of 02 gas = 32 g
molecular mass of 02 gas = 32 g/mol
so, no of moles of 02 gas, 1 = 32/32 = 1 mol
similarly, given mass of CO2 gas = 44g
molecular mass of CO2 gas = 44 g/mol
so, no moles of CO2 gas, n2 = 44/44 = 1
now, V1/V2 = 1/1 = 1
Therefore, the ratio of volumes occupied by 32g 02 and 44 g CO2 at 270C temperature and 700 mm Hg pressure is 1: 1.
Or, A fixed mass of a gas occupies a volume of 520cm3 at -13°° temperature. Keeping the pressure unchanged, when the gas is heated the volume of the gas increases to 700 cm3. What is the final temperature of the gas in degree Celsius?

3.3 Mention two features of the image formed by a simple camera.
Ans: The following are the two features of the image formed by a simple camera:
i) A permanent image is formed on the film.
ii) Image film can be used only once.

Or, Where in front of a concave mirror image of an extended object placed at infinity will be formed by the mirror?
Mention one feature of the image.
Ans: The image will be formed between focus and centre of curvature in front of a concave mirror.
Feature: Image will be real and inverted.

3.4 Mention one similarity and dissimilarity between electromotive force and potential difference.
Ans: Similarity: It is the work done per unit charge in moving a unit positive charge
E.M.F – It is the potential diffrence across the ends of an battery.
Terminal Voltage: It is the potential diffrence across the two points.

3.5 By giving example of an ionic compound show that its ions do not obey the octet rule.
Ans: Sulfur hexafluoride (SF6) are examples of molecules that deviate from the octet rule by having more than 8 electrons around the central atom.

Or, Explain why the melting point of sodium chloride is much greater then that of glucose.
Ans: The melting point of sodium chloride is much greater than that of glucose because sodium chloride is an ionic compound and the melting point of ionic compound are very high as the compounds have strong electrostatic force of attraction.

3.6 Show that F forms ionic bond with Na but it forms covalent bond with H.
(The atomic numbers of H, F, and Na are 1, 9, and 11 respectively)

3.7 Write, with the balanced chemical equation, what happens when nitrogen gas is passed over calcium carbine at 1100°C.
Ans: CaC2 + N2 CaCN2 + C

3.8 Write, with the balanced chemical equation of the reaction for the formation of metallic iron from ferric oxide by thermite process. Write an application of the process.
Ans: Fe2O3 + 2Al = Al2O3 + 2Fe↓
Application of thermite process: With the molten iron broken rail or broken part of instruments can be repaired.
Or, Write, with balanced chemical equation of the reaction that occurs when a piece metallic iron is added to an aqueous solution of CuSO4. What information is obtained from this reaction about the relative position of Cu and Fe in the activity series of metal?

3.9 Select the members of a homologous series from the following compounds and arrange them in increasing order of their molecular weights: CH3 COOH, CH3 CH2 OH, CH3 OCH3, CH3 OH, C2 H4, C2 H6, CH3 CH2 CH2 OH, C3 H4
or, Write with an example what is meant by functional group.
Ans: Functional group is an atom or group of atoms, the presence in which in organic compounds control its chemical properties.
Ex: Hydroxy
Formula:  – OH, Structure:  – O – H


4. Answer the following questions.
4.1 State Avogadro’s law. At a certain fixed temperature and pressure and the molar volumes (V/n) of the real gases are nearly equal and at STP the limit is 22.4 L mol-1. How Avogadro’s law can be arrived at from this information obtained from experiments?
Ans: Avogadro’s law states that, Under the same conditions of temperature and pressure, equal volume of all gases(elementary or compound) contain equal number of molecules.

4.2 A and B react to produce C according to the following chemical equation 2A + B 2C A, B and C are the formulas for three gaseous substances. The vapour densities of A and B are 32 and 16 respectively. Find out the vapour density of C. According to the following chemical equation 2ZnS + 302 2ZnO + 2 SO2 from 100 mole of ZnS
(i) how many gram of ZnO, and (ii) how many mole of SO2 will be produced ?

4.3 Give an example of the volume Expansion of a liquid on heating. The area of a solid substance at a temperature of T1 K is A1 sq m and that at a temperature of T2 K is A2 sq m. Write down the mathematical expression for the coefficient of area expansion with the unit, of that solid substance.
Or, Write down the three factors on which conduction of heat through a solid substance depends.

4.4 What is dispersion of light? Will there be dispersion of white light within a glass slab after refraction when white light is incident on the glass slab at an angle of 45°?
Ans: The phenomena of splitting of white light into its component seven colour is called dispersion of light.
No, dispersion of light does not take place with in a glass slab.

4.5 The principal section of a prism is an equilateral triangle. If a ray of light is incident at an angle of 30° on one of the refracting surface and emerges at an angle of 45° from the other surface, what is the angle of deviation?
Or, What will be the velocity and wavelength of light in a medium of refractive index 1.5 if the wavelength of that light is 6000°A in the air medium?
Ans: In air velocity of light is 3×108 m/s and wavelength is 6000Ao
 =6000×10−10 m
We know that c=λ×f , f=frequency
3×108 =6000×10−10 ×f
We know that refractive index n=
Velocityoflightinvacuum/velocityoflightinmedium = c/v
Here c=3×108
So 1.5=v3×108⟹v=2×108 m/s
Since frequency does not change when light enters from one medium to other.
2×108 =λ×5×1014
λ=4×10−7 m

4.6 Two metallic conductors A and B of the same length have a resistivity of 1.6 into 10-8 Ωm respectively. These two conductors are separately connected to the same potential cross-sections in order to have the same current flowing through each of them?
Or, the series combination of two 10 ohm resistance is connected in parallel combination with a 20-ohm resistance of the final combination.
Ans: Equivalent resistance (series): sum of two 10 ohm resistors = (10 + 10)ohm = 20ohm
Equivalent resistance (parallel): 10ohm [ formula: 1/Rp = 1/R1 + 1/R2]

4.7 What is meant by electrical power ? The rating of a bulb is written as 220V – 100W- what is its meaning?
Ans: Electrical power is the amount of electric energy  consumed or delivered in a circuit per unit time.
The meaning of the statement is this that if we provide 220v of potential diffrence across the ends of the  bulb then the bulb will consumes 100 jolues of energy per second.

4.8 From which part of the atom are the radioactive rays emitted ? which of the radioactive rays has the highest penetrating power and which has the highest ionising power?
Ans: From the nucleus of the atom, radioactive rays are emitted.
Highest penetrating power: γ-ray
Highest Ionising power: α-ray.

4.9 Mention the dissimilarity of properties of hydrogen with one property of group one element and two properties of group 17 elements.
Or, Arrange as directed:
(a) Na (11), K(19), Li (3), Rb(37), belonging to group 1 of the long periodic table according to decreasing order of atomic radius.
(b) S(16), O(8), Te(52), Se(37), belonging to group 16 of the long periodic table according to increasing order of electronegativity.
(c) Ca (20), Be (4), Sr (38), Mg (12), belonging to group 2 of the long periodic table according to decreasing order of reducing power.
(The atomic numbers have been given within the first bracket after the symbol of the element)

4.10 On what basis electrolytes have been classified as strong and weak electrolytes? Give example of a strong electrolyte.
Ans: On the basis of Dissociation capability, electrolytes have been classified as strong and weak electrolytes.
Example of strong electrolyte: NaCl

4.11 Write mentioning the name of catalyst and condition, how nitric oxide is manufacture by oxidising ammonia with the help of aerial oxygen. Write also the balanced chemical equation of the reaction.

4.12 Two different organic compounds A and B have the molecular formula of C2H6O. A reacts with metallic sodium to produce hydrogen gas but B does not react with metallic sodium. Write structural formulas of the compounds A and B. Write the balanced chemical equation of the reaction of A with metallic sodium.
Or, Write the condition for the reaction of the addition of hydrogen to ethylene. Write the balanced chemical equation of the reaction. Mention one use of CNG.

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