Science (Class 12) Term 2 Question Paper 2023
1. The electron dot structure of chlorine molecule is :
2. The name of the salt niced to remove permanent hardness of water is :
3. Sodium hudroxide is termed an alkali while Ferric hydroxide is not because:
(a) Sodium hydroxide is a strong base, while Ferric hydroxide is a weak base.
(b) Sodium hydroxide is a base which is soluble in water while Ferric hydroxide is also a base but it is not soluble in water.
(c)Sodium hydroxide is a strong base while Ferric hydroxide is a strong acid.
(d) Sodium hydroxide and Ferric hydroxide both are strong base but the solubility of Sodium hydroxide in water is comparatively higher than that of Ferric hydroxide.
4. Acid present in tomato is :
(a) Methanoic acid
(b) Acctic acid
(c) Lactic acid
(d) Oxalic acid
5. A metal ribbon ‘X’ bums in oxygen with a dazzling white flame forming white ash the accurate description of X Y and the type of reaction is:
6. When aqueous solutions of potassium iodide and lead nitrate are mixed.on insoluble substance separates. out, The Chemical equation for the reaction involved is :
7. When Sodium bicarbonate reacts with dilute hydrochloric acid, the gas evolved is.
(a) Hydrogen; it gives a pop sound with a bumping match stick.
(b) Hydrogen; it turns lime water milky.
(c) Carbon dioxide; it turns lime water milky.
(d) Carbon dioxide; it blows off a bumping match stick with a pop sound.
8. The number of chromosomes in parents and offsprings of a particular species undergoing sexual reproduction remains constant due to the:
(a) doubling of chromosomes after zygote formation.
(b) halving of chromosomes after zygote formation.
(c) doubling of chromosomes before gamete formation.
(d) halving of chromosomes at the time of gamete formation.
9. During adolescence, the reproductive phase starts and:
(a) general growth rate begins to slow down
(b) height becomes less
(e) the body weight is reduced
(d) hair growth decreases
10. Which pair of sex chromosomes will determine a male?
(a) XO
(b) XX
(c) XY
(d) YY
11. One of the events that docs not occur during photosynthesis is
(a) Chlorophyll absorbs solar energy.
(b) Carbon dioxide is released during the process.
(c) Oxygen is released during the process.
(d) Carbon dioxide as absorbed during the process
12. observe the following diagram and identify the process significance from the following
options :
(a) Evaporation: maintains water contents in leaf cells.
(b) Transpiration: creates a suction force which pulls water inside the plant.
(c) Excretion: helps in excreting out waste water from the plant.
(d) Translocation: helps in transporting materials from one cell to another.
13. An alpha particle enters a uniform magnetic field as shown. The direction of force experienced by the alpha particle is :
(a) towards right
(b) towards left
(c) into the page
(d) out of the page
14. The resistance of a resistor is reduced to half of its initial value. It office parameters or the electrical circuit-produced ml the resistor will become :
(a) four times
(b) two times
(c) half
(d) one fourth
15. The correct pattern of magnectic field lines of the field produced by a current carrying circular loop is :
16. Two LED bulbs of 10W and SW are connected in series. If the current flowing through SW bulb is 0.005A, the current flowing through 1OW bulb is:
(a) 0.02A
(b) 0.01A
(e) 30.005A
(d) 0.0025A
Q. No. 17 to 20 are Assertion – Reasoning based questions.
These consist of two statements -Assertion and Reason (R). Answer these questions by selecting the appropriate option given below.
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.
17. Assertion (A): A current carrying a straight conductor experiences a force when placed perpendicular to the direction of the magnetic field.
Reason (R): The net charge on a current carving conductor is always zero.
18. Assertion (A): The inner walls of the small intestine have finger-like projections called villi which are rich in blood-
Reason (R): These will have a large surface area to help the intestine in completing the digestion of food.
19. Assertion (A): In humans, if gene (B) is responsible for black eyes and gene (D) is responsible for brown eyes. then the color of the eyes of the progeny having gone combination Bb, bb or BB will be black only.
Reason (R): The black color of the eyes is a dominant trait
20. Assertion (A): The reaction of Onicklime with water is an exothermic reaction.
Reason (R): Quicklime reacts vigorously with water releasing a large amount or net
SECTION – B
(Verv Short Answer Questions)
21. (1) State the essential function performed by ozone at the higher levels of the atmosphere.
(ii) Why was there a sharp drop in the amount of ozone in the atmosphere in 1980’s.
22. (A) Observe the following diagram and answer the questions following it :
(i) Identify the defect of vision shown.
(ii) List its two causes.
(iii) Name the type of lens used for the correction of this defect.
OR
(B) The color of clear sky from the earth appears blue but from the space it appears black. Why?
23. Two green plants are kept separately in oxygen-free containers, one in the dark and the other in sunlight. It was observed that plants kept in dark could not
survive longer. Give a reason for this observation.
24. Give two reasons, why bile juice is considered to be an important secretion
of liver in the process of digestion ?
25. “Name the hormone secreted in scary situations by animals. Write any three
responses which enable the animal body to deal with it.
26* (A) A student took a small amount of copper oxide in a conical flask and
added dilute hydrochloric acid to it with constant stirring. He observed a change in color of the solution.
(i) Write the name of the compound formed and its colour,
(ii) Write a balanced chemical equation for the reaction involved.
(B) Tho industrial process used off the mentifiedure of east sods involves electrolysis of an aqueous solution of compound X’. In this press, tao gases y a mucous solution of the compound – In this cathode and Z’, which is liberated at the anode, on treatment with dry slaked lime forms a compound “B’. Name X, Y, Z, and B.
SECTION- C
(Short Answer Questions)
27. Write one difference between biodegradable and non-biodegradable wastes. List two impacts of each type of accumulated waste on the environment if not disposed of properly.
28. (A) (i) Why is an alternating current (A.C.) considered to be advantageous over a direct current (D.C.) for the long-distance transmission of electric power?
(ii) How is the type of current used in household supply different from the one given by a battery of dry cells?
(iii) How does an electric fuse prevent the electric circuit and the appliances from possible damage due to short-circuiting or overloading?
OR
(B) For the current-carrying solenoid as shown, draw magnetic field lines and give a reason to explain that out of the three points A, B, and C, at which point the field strength is maximum, and at which point it is minimum?
29. List two differences in the characteristic properties of the virtual images formed by the two types of spherical lenses (concave and convex). How are these characteristics of the two lenses used in the correction of the two common defects of vision namely myopia and hypermetropia?
30. (A) An object is kept at a distance of 1m from a lens of power +2D:
(i) Identify the type of lens.
(ii) Calculate the focal length and distance of the image formed.
OR
(B) Define the following terms in the contest of a diverging lens:
(i) Principal focus,
(ii) Focal length.
Draw a labelled ray diagram to illustrate your answer.
31. (A) (i) How does Paramecium obtain its food?
(ii) List the role of each of the following in our digestive system:
(a) Hydrochloric acid
(b) Trypsin
(c) Muscular walls of the stomach
(d) Salivary amylase
OR
(B) (i) What is double circulation?
(ii) Why is the separation of the right side and the left side of the heart useful? How does it help birds and mammals?
32. (i) Why is acidified water considered to be a good conductor of electricity?
(ii) Write a chemical equation showing the ionic products formed on dissolving potassium hydroxide in water.
(iii) Care must be taken while diluting concentrated nitric acid with water. Why?
33. (i) While electrolyzing water before passing the current some drops of an acid are added why? Name the gases liberated at the cathode and anode. Write the relationship between the volume of gas collected at the anode and the volume of gas collected at the cathode.
(ii) What is observed when silver chloride is exposed to sunlight? Give the type of reaction involved.
SECTION – D
(Long Answer Questions)
34. (i) How is electric current related to the potential difference across the terminals of a conductor?
Draw a labeled circuit diagram to verify the relationship.
(ii) Why should an ammeter have low resistance?
(iii) Two V- I graphs A and B for series and parallel combinations of two resistors are as shown. Giving reason state which graph shows
(a) series, (b) parallel combination of the resistors.
35. (i) Name and explain the two modes of asexual reproduction oberved in hydra.
(ii) What is vegetative propagation? List two advantages of using this technique.
36 (A) (i) It is observed that covalent compounds are bad conductors of electricity. Give reason.
(ii)Carbon can neither form C cation nor C* anion. Why?
(iii)fit Draw the electron dot structure of Ethanol.
(iv) Identify hetero atom(s) in the following compounds:
OR
(B) What are soaps? Explain the mechanisms of the cleansing action of soap with the help of a labeled diagram.
(ii) Detergents are better than soaps. Justify.
SECTION – E
(Source Based/Case-Based Questions)
37. The ability of a medium to refract light is expressed in terms of its optical density. Optical density has a definite connotation. It is not the same as mass density. On comparing the two media, the one with the large refractive index is an optically denser medium than the other. The other medium with a lower refractive index is optically rarer. Also, the speed of light through a given medium is inversely proportional to its optical density.
(i) Determine the speed of light in a diamond if the refractive index of the diamond with respect to vacuum is 2.42. The speed of light in a vacuum is 3×10* m/s.
(ii) Refractive indices of glass, water, and carbon disulfide are 1.5. 1.33 and 1.62 respectively. If a ray of light is incident in these media at the same angle (say @), then write the increasing order of the angle of refraction in these media.
(iii) (A) The speed of light in glass is 2×10 m/s and in water 5 2,25×10 m/s.
(a) Which one of the two is optically denser and why?
(b) A ray of light is incident normally at the water-glass interface when will happen to the path of the ray after entering the glass? Give reason.
OR
(iii) (B) The absolute refractive indices of water and glass are 4/3 and 3/2 respectively. If the speed of light in glass is 2×10 m/s, find the speed of light in (i) vacuum and (ii) water.
38. The most obvious outcome of the reproductive process is the generation of individuals of similar design, but in sexual reproduction, they may not be exactly alike. The resemblances, as well as differences, are marked. The rules of heredity determine the process by which traits and characteristics are reliably inherited. Many experiments have been done to study the rules
of inheritance.
(i) Why an offspring of a human being is not a true copy of his parents in sexual reproduction?
(ii) While performing experiments on inheritance in plants, what is the difference between F, and F, generation?
(iii) (A) Why do we say that variations are useful for the survival of a species over time?
OR
(iii) (B) Study Mendel’s cross between two plants with a pair of
contrasting characters.
RRYY x rryy
Round Yellow Wrinkled Green
He observed 4 types of combinations in F2 generation. Which of these were new combinations? Why do new features which are not present in the parents, appear in F2 generation?
39. The melting points and boiling points of some tonic compounds are given below :
